Chapter XXVIII: Introduction (24)

This genus is very remarkable amongst sessile cirripedes, from the eight normal compartments of the shell being surrounded by several whorls of supplemental compartments or scales: these are arranged symmetrically, and decrease in size but increase in number towards the circumference and basal margin. A well preserved specimen has a very elegant appearance, like certain compound flowers, which when half open are surrounded by imbricated and graduated scales. The Chthamalinæ, in the structure of the mouth and cirri, and to a certain extent in that of the shell, fill up the interval between the Balaninæ and Lepadidæ; and Catophragmus forms, in a very remarkable manner, the transitional link, for it is impossible not to be struck with the resemblance of its shell with the capitulum of Pollicipes. In Pollicipes, at least in certain species, the scuta and terga are articulated together--the carina, rostrum, and three pairs of latera, making altogether eight inner valves, are considerably larger than those in the outer whorls--the arrangement of the latter, their manner of growth and union,--all are as in Catophragmus. If we, in imagination, unite some of the characters found in the different species of Pollicipes, and then make the peduncle so short (and it sometimes is very short in _P. mitella_) that the valves of the capitulum should touch the surface of attachment, it would be impossible to point out a single _external_ character by which the two genera in these two distinct families could be distinguished: but the more important differences in the arrangement and nature of the muscles which are attached either to the opercular valves or surround the inside of the peduncle, would yet remain.

Although all the valves of the shell, even the eight in the innermost whorl, are very thin, yet from their number in the successive whorls, and from each being concave inwards, so as to form a cavity or tube into which the corium enters, the total thickness of the sides of the shell is very considerable. Both of the species of Catophragmus occurred mingled, in the one case with _Tetraclita porosa_ and in the other with _T. purpurascens_; now the walls of these shells, we know, are very thick, and are permeated by several rows of pores, occupied by threads of corium; seeing this, we may be permitted to believe, that the several exterior whorls of valves in Catophragmus, between which the corium is prolonged for some way upwards, are of service to the animal, by thickening its shell, in an analogous, but not homologous, manner, as in Tetraclita.

Considering the whole structure, external and internal, of Catophragmus, with the one great exception of the exterior whorls of valves, there is hardly a single generic character by which it can be separated from Octomeris and Pachylasma; indeed, I am not quite sure that it would not have been better to have run these three genera together.

Of the two species, I will first describe _C. polymerus_, and not the _C. imbricatus_ of Sowerby, inasmuch as I have plenty of excellent specimens of the former, whereas the original specimens of _C. imbricatus_, in the British Museum, consist of one old and not perfect shell, without the opercular valves or the included animal's body; and the other, though quite perfect, far from mature. As far as these materials allow of minute comparison, the whole shell, with the exception of the basis, and the opercular valves agree very closely in the two species, whereas the included animal's body differs more than is usual in nearly related species;--thus, _C. imbricatus_ has caudal appendages, of which there is no trace in _C. polymerus_, and I have seen only one other instance in which this organ was absent in one species (_Scalpellum villosum_) and present in the other species of the same genus. Under these circumstances it will be most convenient first to describe in detail _C. polymerus_, and then only indicate the points of difference in _C. imbricatus_.

1. CATOPHRAGMUS POLYMERUS. Pl. 20, fig. 4 _a_-4 _e_.

_Basis membranous: caudal appendages none._

_Hab._--New South Wales (Twofold Bay), Mus. Darwin; Swan River (?),
Mus. Cuming. Attached to littoral rocks and shells, and associated
with _Tetraclita purpurascens_, _Balanus nigrescens_, _Chthamalus
antennatus_, _Chamæsipho columna_.

_General Appearance._--Shell nearly circular, moderately or slightly
depressed; colour gray. The eight normal compartments of the inner
whorl are two or three times as large as those in the second whorl;
the other smaller compartments or scales graduate very regularly in
size, to mere beads, at the extreme basal edge, and are arranged
symmetrically. The general aspect of the shell depends chiefly on
the degree to which the surface has been disintegrated, and differs
greatly in the two extreme states. When well preserved, the general
appearance is very elegant; the scales are all neatly imbricated;
they terminate upwards in points, but with their extreme tips
generally broken; from laterally overlapping each other, their
external surfaces (as seen, when corroded, in fig. 4 _d_, or when
slightly exposed after the continued growth of their basal margins,
in fig. 4 _a_) become longitudinally keeled, often with a secondary
ridge or shoulder on one side; they are, also, crossed by rather
conspicuous and regular lines of growth, or more strictly, former
lines of union between the several valves: the orifice of the shell
in this perfect condition is sub-rhomboidal and notched, and the
scuta are united to the terga by nearly straight sutures. On the
other hand, when the shell has been considerably corroded, and this
seems to be the more common condition, the appearance is not elegant:
the scales in the successive whorls are not imbricated, but owing to
their upper parts having been worn down, they present a tesselated
surface (4 _d_), with the tesseræ graduated in size, and of a
peculiar shape, namely, a rectangle, with a more or less broad square
projection on the exterior side, together often with a large square
notch on one or both corners, caused by their laterally overlapping
each other. Some of the shells are so deeply corroded, that no
portion of the original surface is preserved, excepting the lowermost
bead-like scales; and the whole shell has so rugged an aspect,
that the successive whorls of the worn-down valves might easily be
overlooked. In the corroded specimens, the orifice approaches to
circular in outline, and is large and nearly entire: the scuta and
terga are deeply interlocked together. The largest specimen which I
have seen was one inch and a quarter in basal diameter.

_Structure of the Shell._--The eight inner normal compartments are
not thicker than the outer valves, and are far thinner than in
ordinary sessile cirripedes. They are arranged as in Octomeris.
The lateral compartments are broader than the rostro-lateral and
carino-lateral compartments. The shelly laminæ, of which these
compartments and the opercular valves are composed, alternate with
yellow membranous layers, exactly as is the case with Octomeris.
The lateral edges of the compartments, beneath the alæ, in the six
compartments having alæ, bend inwards, especially just above the
basis, so that the compartments in their lower parts (fig. 4 _c_)
stand much more separate than is usual. The basal edge of each is
irregularly toothed. The sheath presents no particular character.
The eight compartments have longitudinal shoulders and ribs on their
external surfaces, caused by the lateral overlapping and pressure of
the exterior scales. They are also marked by slight, transverse or
oblique calcareous ridges, caused by the attachment of the membrane,
by which they are united to the smaller compartments or scales
outside them. A new line of attachment, and consequently a new ridge
is formed, lower and lower down at each period of growth, as the
shell is added to at the basis,--in the same manner as new ridges are
added to the lower edge of the sheath at each period of growth. The
shell, excepting in old worn-down specimens, increases largely by
diametric growth: during the diametric growth, the outer scales must
be laterally separated a little from each other, and probably they
are laterally added to; but there are no distinct lines of suture,
or rows of smaller scales, corresponding with the sutures between
the eight inner compartments. The alæ do not project much; their
edges, as well as the shoulders into which they fit, are generally
irregularly crenated: they are added to during diametric growth
above the line of attachment of the opercular membrane. There is no
appearance of radii; but as the eight inner compartments are added to
laterally, and are often crenated, on the edges which correspond with
the radii in other Cirripedes, such edges must be considered as radii.

With respect to the scales in the several outer whorls, they resemble
each other except in size, and the outermost scales are reduced to
mere transversely elongated beads. Their basal edges are concave
inwards, being bent like the ridge of a house; hence sub-triangular
spaces or tubes, lined by the corium, run up between the scales. When
perfectly preserved, the outline of each scale is a much elongated
triangle, but usually, from their summits having been worn off, the
outline is nearly that of a parallelogram. Their basal edges are
dentated, and their upper parts, both on the outside and inside, are
marked, where joined to the other compartments, by slight calcareous
ridges: outside, there are longitudinal shoulders (Pl. 20, fig. 4
_b_), caused by the lateral overlapping of the adjoining scales;
these are best seen in section in corroded specimens (fig. 4 _d_):
on the inside there are, also, in the upper part, slight medial
longitudinal ridges, caused by the sutures, which the scales have
covered.

In large old specimens there are ten, or even more, whorls of
compartments, but it is scarcely possible to count them with
any accuracy. The first whorl consists of the eight large inner
compartments, though, homologically, it is doubtful whether the
rostro-lateral compartments in any sessile cirripede really belong
to the same whorl with the others. The second whorl consists of
eight smaller pieces, covering the eight sutures in the first whorl
(see the tracing of the basal edges of all the compartments and
valves in a very perfect specimen, Pl. 20, fig. 4 _c_). The third
whorl, in large and perfect specimens, consists of twice the number,
or sixteen, still smaller scales, corresponding with the sixteen
sutures of the second whorl; but sometimes there are less than
sixteen pieces, owing to some of the scales being large enough to
cover two adjoining sutures as well as the intermediate portion of
the compartments of the first whorl. In the fourth whorl, instead
of there being, even in the most perfect specimens, twice sixteen,
or thirty-two pieces, there are only twenty-four; this being caused
by single pieces (placed alternately with two pieces) being broad
enough to cover two sutures as well as the intermediate portion of
the compartment of the third whorl. In the succeeding whorls this
same arrangement seems to be the usual one, so that in the fifth
whorl, instead of there being, in the most perfect specimens, twice
twenty-four, or forty-eight pieces, that is, twice the number in the
last whorl, there are only thirty-six scales, or once and a half as
many scales.

The _Basis_ is thin and membranous; it firmly adheres to the surface
of attachment.

_Scuta_, nearly flat: the articular ridge is very prominent, and
there is a deep articular furrow both above and below; but the
precise outline of the ridge and furrows varies: there is a pit
for the adductor muscle, but no crests or marks for the other
muscles. The _Terga_ are remarkable from the extreme prominence of
the articular ridge and depth of the articular furrow. The basal
margin viewed internally seems straight, so that there appears to be
no spur; but viewed externally, when the crests for the depressor
muscles are seen to depend considerably beneath the true basal
margin, a slight, very broad spur may be perceived to exist. These
depending crests for the muscles are rather thin, but they extend
over half the basal margin of the valve.

_Mouth._--The labrum is very bullate, being as long in its
longitudinal axis as the rest of the mouth: crest hairy, with some
very minute teeth. Palpi truncated, with their apices not nearly
touching each other; thickly clothed with spines. Mandibles with
three large single teeth, of which the lower one has a single
fine tooth at its upper basal edge, showing a tendency to become
pectinated; inferior part short, coarsely pectinated. Maxillæ
notched, with a slight second notch and slight double prominence in
the lower part.

_Cirri._--First and second pairs short, with the rami in each
unequal in length by about four segments; on both rami in the second
cirrus, and in the shorter ramus of the first cirrus, there are some
coarsely pectinated spines. All four posterior cirri are alike; the
segments bear five pairs of strong spines, with a large intermediate
tuft of fine spines: the dorsal tuft is also large, consisting of
short thick, and long finer spines. There is no vestige of _caudal
appendages_, though present in the succeeding species.

Branchiæ moderately large, in area equalling the prosoma; surface not
plicated.

2. CATOPHRAGMUS IMBRICATUS.

CATOPHRAGMUS IMBRICATUS. _G. B. Sowerby._ Genera of Recent and Fossil
Shells, Plate.

_Basis calcareous: caudal appendages present._

_Hab._--Antigua, West Indies, attached to a _Tetraclita porosa_.

As stated under the genus, this species is known from two specimens
in the British Museum, one of which is full-sized, being three
quarters of an inch in diameter, but is destitute of the outermost
whorls, of the basis, opercular valves, and animal's body; the other
is perfect, but very young, being barely two tenths of an inch in
basal diameter. As far as the characters can be made out from these
materials, I can perceive no difference from _C. polymerus_ in the
shell, excepting that in the small specimen of _C. imbricatus_, there
would appear to exist fewer whorls. The opercular valves are likewise
closely similar: in the scuta, however, of the young specimen in the
present species, the articular ridge seems to be a little broader,
but this is so variable a character that no confidence can be placed
in it: these valves, moreover, externally have a broad furrow along
the middle, running from the apex to the basal margin, which is not
the case with the scutum of _C. polymerus_; but then I have often
seen, in young specimens of Balanus, a similar furrow, which is quite
absent in full-grown specimens. When we come to the basis we find a
good diagnostic character, for here it is calcareous: it is rather
thin, solid, and white; towards the outside it is pitted with small
cavities, corresponding with the small teeth on the basal edges of
the compartments. The latter adhere firmly to the basis. The central
internal surface is covered by an irregular network of imbedded
cement-ducts, some of which bifurcate. From the description here
given, it will be seen that any figure would have been superfluous,
the last species having been so well illustrated.

_Mouth._--I can point out no difference, excepting that the palpi are
here more oval or less truncated at their ends; and that the lower
corner of the maxillæ seems to be more prominent. In the _Cirri_, the
rami of the first and second pairs are nearly equal in length: none
of the spines are coarsely pectinated. In the four posterior pairs
of cirri, instead of a tuft of small spines on each segment between
the pairs of main spines, there are only a few minute intermediate
spines: the dorsal tufts are also here smaller, but are, as in the
last species, composed of short thick, and longer thinner spines.

_Caudal Appendages._--This is the only species of sessile cirripede,
with the exception of the two species of Pachylasma, which possesses
these organs: they are situated on each side of the anus in the usual
position: they are minute, equalling in length only the lower segment
of the pedicel of the sixth cirrus: in a specimen in which the rami
of the sixth cirrus had eighteen or twenty segments, these appendages
consisted of only three tapering segments, supporting a few thick
spines.

_Branchiæ._--I believe I discovered these, consisting of two minute
pouches, placed at the carinal end of the sack: if this observation
be correct, this species differs from _C. polymerus_ in the much
smaller size of these organs.

REMARKS ON BRONN'S LIST OF FOSSIL BALANINÆ AND CHTHAMALINÆ.

The following species of fossil Balanidæ are given in that most
useful work, the 'Enumerator Palæontologicus' in Bronn's 'Gesichte
der Natur:' it has appeared to me that a few words on each species,
might hereafter save others the trouble of searching through several
works.

_Tubicinella maxima_ of Morren, said to have been found in the Chalk:
this would have been a wonderful fact, considering that no true
sessile cirripede has hitherto been found in this formation, and that
it implies the existence of Cetacea at this period; but I have been
informed that the fossil in question is not a Cirripede.

_Diadema bifidum_ = Coronula bifida of Bronn, in his 'Italiens
Tertiär-Gebilde' (1831), p. 126 (no Plate). Without a much fuller
description I can form no judgment on this species.

_Diadema vulgare_ is probably the _Coronula barbara_, a Crag fossil
described by me.

_Pyrgoma undata_, Michelotti, in 'Bull. Soc. Geolog.' tom. x, p. 141,
a mere name without any description: probably it is a synonym of

_Pyrgoma sulcatum_, Philippi, 'Enum. Mollusc. Siciliæ,' which is a
synonym of _Pyrgoma Anglicum_ of the present work; found recent and
fossil.

_Acasta Montagui_ is probably the extinct _Acasta undulata_ described
by me.

_Chthamalus giganteus_ of Philippi, is the _Pachylasma giganteum_ of
this work; found recent and fossil.

_Chthamalus stellatus_, said by Philippi to be found fossil in
Sicily; such may be the case, but the littoral habits of the species
do not render it very probable.

_Balanus carbonarius_ of Petzholdt, found in the Carboniferous
formation! but I have given my reasons, in my 'Monograph on the
Fossil Lepadidæ,' p. 5, for disbelieving that this is a Balanus, or
even a Cirripede.

_Balanus ostrearum_ appears to be a mere name by Conrad, published
by Morton in his 'Synopsis of the Organic Remains of the Cretaceous
Group,' 1834, Appendix, p. 8.

_Balanus peregrinus_ is briefly described and poorly figured, without
the opercular valves, by Morton, in his 'Synopsis,' _ut supra_, p.
72, Pl. 10, fig. 5: this Eocene species apparently resembles the
Eocene _B. unguiformis_ of Sowerby, described in this work; but quite
indispensable details of structure for identification are not given.
Another figure of this shell is given in the 'American Journal of
Science' (N. S.), vol. i, Pl. 2, fig. 6.

_Balanus circinnatus_, _communis_, and _pustula_, of Defrance,
as well as all the other species named by him, are described so
imperfectly, that the descriptions are of no value whatever, every
description being applicable to every species: I must add, that the
_B. communis_ is not the _B. communis_ of British authors, a name
applied to several forms.

_Balanus Finchii_ is briefly described and figured, but without the
opercular valves, by Isaac Lea, in his 'Contributions to Geology,'
1833, p. 211, Pl. 6, fig. 222. I do not think that I have seen this
species.

_Balanus Holgeri_, Geinitz, 'Grundriss der Versteinerungen,' tab. ix,
fig. 19. No opercular valves are given; this species cannot be even
approximately recognised.

_Balanus proteus_, Conrad, 'Fossil Shells of Miocene Formation of U.
States,' p. 77, Pl. 44 (in 'Journal Acad. Nat. Sc.,' Phil., vol. vii,
p. 134). I cannot recognise this species; it resembles _B. porcatus_;
but as the radii are rather narrow, and apparently with slightly
oblique summits, it may be _B. concavus_; the opercular valves are
not figured.

_Balanus sagittata_ is merely a provisional name without any
description, given in a paper on the Crag by S. Woodward, in the
'London and Edin. Philosoph. Magazine, Brewster, Taylor, and
Phillips,' vol. vii, July-December, 1835, p. 354.

_Balanus sublævis_, J. de C. Sowerby, in 'Geolog. Trans.,' 2d series,
vol. v, Pl. 25, fig. 3. Plate extremely imperfect; description
extremely short and useless; a species from India not to be
recognised.

_Balanus balanoides_; the species thus named by Ranzani, and found
by Philippi in Sicily, certainly is not the true _Lepas balanoides_
of Linn., but may be _B. amphitrite_ of this work. In British
collections of Crag specimens I have found the _B. dolosus_ (nov.
spec.) thus named: I much doubt whether the truly littoral _B.
balanoides_ of Linnæus has been found fossil.

_B. costatus_ of Montagu, a synonym of _B. sulcatus_ of Bruguière,
and of _B. porcatus_ of this work; found fossil and recent. This
species was originally described by Linnæus under the name of _Lepas
balanus_. But the fossil _Lepas balanus_ of Brocchi is a different
species; if it be the same with the recent _Lepas balanus_ of Poli,
then it is the _B. perforatus_ of the present work. Again, the _B.
sulcatus_ of Bronn, in his 'Lethæa Geognostica' (tab. 36, fig. 14),
is quite different from the _B. sulcatus_ of Bruguière (_i. e._,
_B. porcatus_ of the present work), as is at once obvious from the
oblique summits of the radii. Lastly, _B. tesselatus_ of Sowerby is a
synonym of _B. porcatus_, _sulcatus_, _costatus_, and _Lepas balanus_.

_B. punctatus_ of Montagu is a synonym of _Chthamalus stellatus_, see
remarks on that species: the name of _B. punctatus_ is often applied
by British authors to varieties of _B. balanoides_, see remarks on
that species.

_B. rugosus_ of Morris's 'Catalogue' is a synonym of _B. crenatus_;
found recent and fossil.

_B. sulcatus_ of Bruguière, a synonym of _B. porcatus_; found recent
and fossil: see remarks under _B. costatus_.

_B. tintinnabulum_ of Linn., found recent and fossil; but no trust
whatever ought to be placed in the identifications of this species
given in several works; thus the _Lepas tintinnabulum_ of Brocchi is
distinct. The _B. crassus_ of Sowerby is the true _B. tintinnabulum_.
The _B. fasciatus_ of Dujardin (perhaps only a MS. name) probably
is also this species. The _B. crispatus_ is only a variety of _B.
tintinnabulum_.

_B. dentiformis_, Defrance: see _B. circinnatus_.

_B. ornatus_, Münster, 'Beiträge zur Petrifact.,' B. 3, p. 29, tab.
vi (1840). No opercular valves or details of structure of the several
species of Balanus named by Münster, are given, and consequently none
can be recognised with certainty.

_B. concavus_ of Bronn, fully described in this work, with the
synonyms given; recent and fossil.

_B. crassus_ of Sowerby, a synonym for _B. tintinnabulum_.

_B. latiradiatus_, Münster, probably a synonym of _B. tintinnabulum_,
see remarks under _B. ornatus_.

_B. pectinarius_, Bronn ('Italiens Tertiär-Gebilde,' p. 128), does
not appear to me fully enough described to be recognised.

_B. pictus_ of Münster, possibly a synonym of _B. amphitrite_: see
remarks under _B. ornatus_ and _balanoides_.

_B. plicarius_, Bronn: see remarks under _B. pectinarius_.

_B. porosus_ of Hausman (according to Münster of Blumenbach). I
cannot recognise this species in Münster's 'Beiträge.'

_B. pustularis_ of Lamarck, 'Animaux sans Vertèbres.' Scarcely one
of the fossil species of Balanus, described by Lamarck, can be
recognised; the descriptions are extremely imperfect. There is a
figure of _B. pustularis_ in Münster's 'Beiträge,' which makes me
think that this may be a synonym of _B. concavus_ of Bronn.

_B. pyramidalis_, Münster: see remarks under _B. ornatus_.

_B. rhomboicus_, Bronn: see remarks under _B. plicarius_.

_B. squamosus_, Defrance: see remarks under _B. circinnatus_.

_B. stellaris_, Bronn ('Lethæa Geognostica,' tab. 36, fig. 13). To
this species, _Lepas stellaris_ (I presume a misprint for _stellata_)
of Poli, is given as a synonym; but the _Lepas stellata_ of Poli is a
Chthamalus, and this certainly is not the case with _B. stellaris_. I
have received two specimens from the Continent named _B. stellaris_,
but they certainly differed from the form so called by Bronn, for
in that, the parietes are said to be porose and the radii very
narrow: these foreign specimens I have named _B. inclusus_. A species
described by me as _B. corrugatus_, resembles in external appearance
the _B. stellaris_ of Bronn, but it is mere labour in vain to attempt
identifying Balani by their external characters.

_B. striatus_, Defrance: see remarks under _B. circinnatus_.

_B. tertiarius_, Risso, 'Hist. Nat. de l'Europe Merid.,' vol. iv. I
cannot recognise this species.

_B. tesselatus_, Sowerby, a synonym of _B. porcatus_; recent and
fossil: see remarks under _B. costatus_.

_B. zonarius_, Münster: see remarks under _B. ornatus_; possibly this
is a synonym of _B. concavus_.

_B. amphimorphus_, Lamarck: see remarks under _B. pustularis_.

_B. crispatus_, _var._ of _B. tintinnabulum_.

_B. cylindraceus_, Lamarck. From Chenu's 'Illust. Conch.,' in which
work Lamarck's original specimens are figured; it appears that this
is the _B. psittacus_ of South America, where it is also found
fossil, but assuredly Lamarck is quite in error when he states that
a variety of this species occurs fossil near Turin. Bronn (in his
'Italiens Tertiär-Gebilde,' p. 127) gives as a synonym to the Turin
fossil the _Lepas tintinnabulum_ of Brocchi (in the 'Conchologia
Fossile Subapennina,' t. 2, p. 597), and this probably is correct;
and I have hardly any doubt that the _Lepas tintinnabulum_ of Brocchi
is the _B. concavus_ of Bronn described in the present work.

_B. perforatus_ of Bruguière is said by Philippi to be found in
Sicily: see remarks under _B. tulipa_.

_B. semiplicatus_, Lamarck: see remarks under _B. pustularis_.

_B. tulipa_ of Müller is the _B. Hameri_ of this work, under which
name full information on its geological history has been given.
The _B. tulipa_ of Poli and Ranzani is the _B. tulipiformis_ of
the present work; and this latter species is said by Philippi to
occur fossil in Sicily. But there has been so much confusion in
the identification of _B. tulipiformis_, _B. Hameri_, and _B.
tintinnabulum_, and likewise of _B. perforatus_ (which by Poli was
wrongly considered to be _L. balanus_, Linn.), that doubts must be
entertained about which have been really found, until the Sicilian
fossils are all carefully examined.

_B. ovularis_, Lamarck: see remarks under _B. pustularis_.

_B. Uddevallensis_, Linnæus, is probably a synonym of the _B. Hameri_
of this work and the _B. tulipa_ of Müller.

[A few other references may be added to those given by Bronn.]

_B. miser_, stated by Lamarck to be found fossil: see remarks under
_B. pustularis_.

_B. patellaris_ of Lamarck, is stated by Marcel de Serres to be found
fossil with several other species of Balanus; thus named without any
description in the 'Annales des Scien. Phys. et Nat. de Lyon,' tom.
i, p. 417.

_B. virgatus_, _delphinus_, and _crispus_, are names given by
Defrance, with absolutely worthless descriptions.

_B. radiatus_ is too briefly described by Risso ('Hist. Nat. de
l'Europe Merid.,' tom. iv, 1826), without a figure, to be recognised;
it probably is not the _B. radiatus_ of Spengler, Wood, and other
authors.

_B. goissopomo_, _lævis_, and _radiatus_, are mere names without
any description, published in a Catalogue by F. Hoeninghaus, in the
'Jahrbuch für Mineral. Geog.,' &c., 1831, p. 155.

_B. humilis_. Conrad, in the 'American Journal of Science,' vol. ii
(N. S.), p. 400, 1846, has given a short description, with a woodcut,
of this species, from the upper Eocene of Florida. The opercular
valves are not described, and I doubt whether the species could be
recognised.

2. Family--VERRUCIDÆ.

_Cirripedia without a peduncle: scuta and terga, not furnished with depressor muscles, moveable only on one side, on the other side united immoveably with the rostrum and carina into an asymmetrical shell._

The one genus herein contained differs so considerably from all the others in the Order, in the extraordinary unequal development of the two sides of the shell, that I have instituted a Family for its reception. If compelled to place it in one of the foregoing families, I should with much hesitation rank it in the sub-family Chthamalinæ, rather than amongst the Lepadidæ; for it is destitute of a peduncle, and has a shell, though a very different one from that of any true sessile cirripede. In the interfolding sutures which may be considered as representing radii or alæ, in the basis being divided into concentric slips, and in the whole of the basis being attached to the supporting object, this same line of affinity is clearly manifested. On the other hand, in the general shape, manner of growth, and kind of articulation of the scutum and tergum, there is so close an approach to the Lepadidæ, that had I seen these very important valves separately, I should certainly have concluded that they had come from a Pollicipes, allied to certain Cretacean fossil species, as _P. fallax_ and _elegans_; it likewise, perhaps, deserves notice, that the upward growth of the rostrum, in _Verruca nexa_, is a peculiarity found only in the valves of the Lepadidæ. Verruca differs both from the Lepadidæ and Balanidæ in the whole shell or external covering, having no other muscle besides the adductor scutorum. In the characters derived from the animal's body, Verruca approaches both families; but in the absence of branchiæ, and in the great development of the caudal appendages, perhaps it comes rather the nearest to the Lepadidæ. Whatever affinity there is to the Balanidæ, it is much stronger to the sub-family Chthamalinæ than to the Balaninæ; though the non-bullate labrum, in three of the species, and the great dissimilarity of the third cirrus from the three posterior pairs, at first seems to indicate a closer relationship to the Balaninæ; but the labrum is never notched, as in the latter sub-family, and in _V. nexa_ it is bullate, and supports palpi of only small size. The dissimilarity, also, of the third pair of cirri, compared with the posterior pairs, is hardly greater than in _Chthamalus intertextus_ and _Chamæsipho columna_, members of the Chthamalinæ, though abnormal in this one respect. Perhaps even a special affinity is evinced between certain species of Chthamalus, as _C. intertextus_, and certain species of Verruca, as _V. nexa_, namely, in the interfolding sutures and in the very peculiar, inflected basal margin of the walls. Upon the whole, the affinities of the Verrucidæ are complex, and nearly equally divided between the two great families of Balanidæ and Lepadidæ, or sessile and pedunculated cirripedes.

_Genus_--VERRUCA. Pl. 21.

VERRUCA.[136] _Schumacher._ Essai d'un Nouveau Syst. Class., 1817.

CLYSIA. _Leach._ Journal de Physique, tom. 85, July, 1817; _Clisia_,
Leach, Encyclop. Brit. Suppl., vol. 3, 1824; _Clitia_, G. B.
Sowerby, Genera of Recent and Fossil Shells.

CREUSIA. _Lamarck._ Animaux sans Vertèbres, 1818.

OCHTHOSIA. _Ranzani._ Memoire di Storia Nat., 1820.

LEPAS ET BALANUS AUCTORUM.

[136] According to Bock, in the 'Naturforscher' of 1778, this
term was used by Rumph for a Chelonobia, but as it was before the
adoption of the binomial nomenclature, according to the Rules, it
may be passed over, and does not interfere with the priority of
Schumacher.

_Distribution_, Northern Europe, Mediterranean, Red Sea, Madeira,
West Indies, Tierra del Fuego, Chile, Peru.

The shell in this genus is extremely unsymmetrical, not two of the six pieces of which it is composed quite resembling each other. At first it appeared hopelessly difficult to identify, in a homological sense, these six valves, with those of ordinary cirripedes, but the difficulty soon quite vanished. The operculum consists of two moveable valves on one side, namely, a scutum and tergum, but without any moveable valves on the opposed side: the scutum, though remarkable from being much smaller than the tergum, can be easily recognised by giving attachment to the animal's body and to the adductor scutorum muscle. The four other pieces are articulated together, and form the shell surrounding the sack, in which the animal's body is enclosed: of these, the two against which the moveable scutum and tergum shut, are smaller, differ greatly in shape, and are articulated together in a different manner from the remaining two pieces; from these facts alone there would be a strong presumption that they were of a different nature. The fixed valve, against which the scutum shuts, is either furnished with a remarkably prominent plate (_a_ in fig. 1 _c_, _s′_; compare this with _s′_ in the reversed shell in fig. 1 _e_), or is hollowed out, as in _V. nexa_, for the attachment of the adductor scutorum muscle. Thus it is rendered probable that this fixed valve is a modified scutum; but a surface of attachment for one end of the adductor muscle might, perhaps, have been developed on any other valve, or a scutum might have become fused with a lateral valve of the shell; the shell on this latter view being rendered in idea more symmetrical. But when a very young specimen is carefully examined, it is found that the moveable and fixed scutum, the moveable tergum and its opposed valve or fixed tergum, at the first period of calcification, resemble each other quite closely; but that, as each zone of shell is added, the differences become rapidly greater and greater: hence, it may be considered as directly proved, that the two fixed valves (S′ and T′ in all the figures in Pl. 21), which are opposed to the moveable valves of the operculum (S and T), consist of an extraordinarily modified scutum and tergum. It has been shown (p. 129), that at the period of the metamorphosis, the two scuta, the two terga, and the carina of the Lepadidæ, commence their growth, under the form of the so-called "primordial valves," and so differ from all the other valves when such occur: now, in two species of Verruca, I have found closely analogous primordial valves on the apices of both the moveable and fixed scutum and tergum (thus affording strong additional evidence that their nature has been rightly interpreted), and on one of the two remaining valves, namely, that at the posterior or carinal end of the shell. Hence, we may safely infer, that this latter valve, which, though very much more developed on one than on the other side, is so far medial as to curl round and cover the line of opening between the moveable and fixed tergum, is really a carina. The sixth valve differs only very slightly in shape from the carina, and is directly opposed to it; therefore, in accordance with all analogy, it must be the rostrum. Consequently, the shell in Verruca consists of a moveable scutum and tergum, a fixed scutum and tergum, a carina and rostrum, and, as we shall immediately see, a membranous basis--the basis being, as in all sessile cirripedes, the homologue of the peduncle in the Lepadidæ.

The moveable scutum and tergum stand at about right angles with the fixed pair; and as these latter form a part of the wall of the shell, which is always steep on this side, the moveable pair, which close the orifice, are nearly horizontal or parallel to the basis and surface of attachment. Hence, the animal's body, which is attached between the two scuta, but nearest to the moveable scutum, also, lies nearly parallel to the surface of attachment; and I was consequently at first led to suspect that the basal membrane was one side of the shell in a modified condition; but the presence of the prehensile antennæ of the pupa in nearly the middle of this membrane, and the sheet of cement-tissue on its under side, demonstrate that this membrane, though lying on one side of the animal, is the true basis. To make all the parts in Verruca hold the same position as in other cirripedes, relatively to the surface of attachment, we must develope the carina and rostrum equally on both sides of the true longitudinal axis of the shell, and insert the newly-developed portion between the basis and the fixed scutum and tergum, reducing the latter in size, and tilting a little up the moveable scutum and tergum; and by this means the animal's body would be turned, so that its dorso-ventral longitudinal plane would stand at right angles to the basal membrane.

Extraordinarily great as is the difference between the right and left sides of the whole shell, yet in all the species it seems to be entirely a matter of chance whether it be the right scutum and tergum with the right side of the rostrum and carina, or the left scutum and tergum with the left side of the rostrum and carina, which become abnormally developed. Nor does there seem to be any relation between the side of the operculum to be attached, whether right or left, and the nature of the surface of attachment; for I have seen many specimens adhering to perfectly level surfaces, and to quite cylindrical branches of Laminariæ; and in these cases, however the larva might attach itself, there could be nothing to favour the development of one side more than the other. Although the attached scuta and terga are larger than the moveable pair, yet, owing to the small development of the carina and rostrum on the attached side, the upper or unattached side must be considered as the most developed. In this respect, and in the circumstance of either right or left side being modified, we are reminded of the structure of _Pœcilasma Kæmpferi_ (described in my former volume on the Lepadidæ), in which the valves on the side of the capitulum, nearest to the crab's body, to which the specimens were attached, were somewhat less developed than those on the opposite side. I may add, that in ordinary Crustaceans, as I am informed by Professor Bell, the unequal development of the thoracic limbs seems quite capriciously to affect either the left or right side of the body.

_General Appearance of the Shell._--The shell is in most cases much depressed and irregularly circular; the side formed by the fixed scutum and tergum is always steeper than the other side: the colour is white or pale brownish, and in _V. nexa_ pale red. The surface is naked. The size is small, rarely exceeding a quarter of an inch in diameter, and the whole shell often appears like a mere scale on the surface of attachment. The most remarkable feature in the external aspect is due to the suture between the rostrum and carina, which is formed by oblique, interlocking plates or folds; as all these plates continue to be added to at their extremities during growth, the upper plates become longer than the lower ones; and the plates on both sides of the suture together form a triangular area, with the broad end uppermost, somewhat like the radius of a sessile cirripede: they act, also, like a radius, for their growth serves to separate these two valves, and so adds to the diameter of the shell. The suture between the rostrum and fixed scutum and that between the carina and fixed tergum are nearly of the same nature, but the former is more conspicuous than the latter; neither are so conspicuous as that between the carina and rostrum: accordingly as the right or left scutum and tergum are moveable, so the suture, second in plainness, (see Pl. 21, fig. 1 _a_, and 1 _d_,) is placed to the left or right hand. The fourth suture, between the fixed scutum and tergum, as viewed externally, is straight, and so very obscure that it has been overlooked by some authors, and the shell described as consisting of only three nearly equal pieces, for the fixed scutum and tergum together are about equal in size to the carina or rostrum. The orifice approaches more nearly to an unequal-sided triangle, with the apex broadly truncated, than to any other figure. The operculum fits with remarkable closeness, and is surrounded by a slight rim, formed by the edges of the four other valves.

_Moveable Scutum and Tergum._--The scutum (S in 1 _b_ and 5) is narrow and very small, barely equalling half the size of the tergum, and therefore proportionally much smaller than in any other cirripede; in a very young shell, however, (of _V. Strömia_) less than a pin's head in size, the scutum equalled the tergum in size. The valve is remarkably thick; it is generally depressed down the middle; but in _V. nexa_ this part is longitudinally ribbed. The occludent margin is curved. On the tergal margin there are two articular ridges (with a deepish furrow between them), of which the upper one (′ in S, in fig. 1 _b_, and 5) extends from the apex about half-way down the valve; and the other, or lower articular ridge (′′ in S), generally runs down nearly to the basal margin: an angle, running from the apex to the basi-tergal corner of the valve, appears like a third articular ridge, but cannot properly be considered such. The above two articular ridges interfold with analogous ones on the scutal margin of the tergum, and so lock the valves together. On the under side (fig. 1 _f_), the surface is bounded along the occludent margin by a slight rim: there is generally a very slight depression for the adductor muscle; but in _V. Spengleri_ there is a straight, short, sharp (Pl. 21, fig. 2), prominent adductor ridge.

The _moveable tergum_ is broad and rhomboidal. Externally a prominent axial ridge (′′′ in T, in fig. 1 _b_, &c.), which widens downwards, runs from the apex of the valve to the basal point, and there projecting slightly, causes the scutum to be indented; this indentation on the scutum appears like a third articular ridge, lying beneath (′′), S, in fig. 1 _b_, &c. Above the lower and axial ridge, on the scutal margin of the tergum, there is a middle articular ridge, which locks in, between the lower (′′) and upper articular ridges (′) of the scutum (S). Again above the middle ridge there is an upper and third articular ridge (′), which is either quite distinct, as in fig. 5, T, or more commonly is formed by the occludent margin of the valve, as in T, fig. 1 _b_. The broad extremity of this upper articular ridge is often produced into a slight projection, or shoulder, and this always underlies the scutum, of which the under and upper surface is indented or furrowed (see fig. 1 _f_), in order to receive this shoulder. The upper articular ridge of the scutum (′, S, 1 _b_) locks in between the upper articular ridge or occludent margin (′, T), and the middle ridge (′′, T) of the tergum.

Hence, altogether, there are three articular ridges on the scutal margin of the tergum, the occludent margin being generally counted as one; whereas, on the tergal margin of the scutum, there are only two ridges, though, as before noticed, an outer indentation, which is developed as a ridge in _V. nexa_ (fig. 5, S), might almost be counted as a third articular ridge.

I may here just remark, that the furrow between the two ridges on the tergal margin of the scutum, resembles the articular furrow in the scutum of the Balanidæ; but it may be doubted whether the resemblance be more than superficial, as this furrow, in the case of Balanidæ, receives the edge itself of the tergum, whereas here it receives only a ridge, proceeding from the apex of the tergum, to a nearly middle point on its scutal margin. Finally, I may add, that the tergum in this genus, in general shape, in growth (presently to be referred to), in the manner in which the upper scutal shoulder is overlapped by the scutum, and in the presence of the axial ridge, presents a very striking resemblance to certain old fossil species of Pollicipes, and to a limited extent to the living species of Lithotrya.

The scutum and tergum being interlocked, move together; they can be firmly shut by the contraction of the long adductor scutorum muscle. Their opening appears partly due to the elasticity of the membranous hinge (representing the opercular membrane), by which they are attached transversely, just beneath the summit of the carina and rostrum. No doubt the protrusion of the cirri effectively aids the act of opening. These valves are not capable (nor, of course, the other valves) of any other movement; for there are no muscles for such movements.

_Fixed Scutum and Tergum._--The fixed scutum is larger than the fixed tergum, and therefore has the same proportions as the homologous valves in ordinary cirripedia, but reversed proportions compared with the moveable scutum and tergum. The shape of neither valve can hardly be described. The _fixed Scutum_ (S′ in all the figs.), externally, seems at first to consist of two portions, namely, a curved occludent rim (_a_), closely resembling the opposed occludent margin (_a_) of the moveable scutum (S), having in fact undergone very little modification, (as may be best seen in Pl. 21, fig. 1 _b_); and secondly, of a much modified portion (marked ′′), which resembles in outline and state of surface the rest of the walls of the shell, and may be called the parietal portion. The rostrum (A) curls round the end of the occludent portion, under an edge (_b_), evidently answering to the basal margin (_b_) of the moveable scutum, and is simply united to this portion by membrane, but beyond this part, it is articulated to the parietal portion (′′) of the fixed scutum, by oblique interlocking ridges, like those forming the suture between the rostrum and carina. In _V. nexa_, however, (fig. 5) the rostrum (A) does not curl round any part of the interlocking fixed scutum (S′), but articulates with it by a straight suture. Internally, the fixed scutum (S′ in figs. 1 _e_, 1 _c_, of reversed shells) has a surprisingly large, thin adductor plate (_m_ in fig. 1 _c_, 1 _b_), with a rounded outline, projecting nearly parallel to the basis or surface of attachment; the adductor scutorum muscle is attached to its upper surface, and consequently the animal's body lies between this plate and the moveable scutum. In the fixed scutum of _V. nexa_, however, there is a deep pit, instead of a plate, for this muscle.

The _fixed Tergum_, likewise, consists of two portions--a middle and lower, or parietal portion, and a rim or upper portion; the rim consists of two unequal arms, answering to the two upper margins (not merely the edges) of the rhomboidal moveable tergum; the longer rim (_x_ in T′, see fig. 5) answers to the carinal margin (_x_) of the moveable tergum, and may be called the carinal rim; and the shorter rim (_o_ and ′ in fig. 5) answers to the occludent margin (_o_ and ′) of the moveable valve, and may be called the occludent rim. The carina curls round the end of the carinal rim, under an edge, _z_ (much foreshortened in T′ in fig. 1 _b_, and best seen in fig. 5), answering to at least a large part of the basal margin (_z_) of the moveable tergum, and interlocks, by a serrated suture, with the edge of the parietal portion of the valve. Internally (fig. 1 _e_, less plain in 1 _c_) there is a transverse ledge, notched in the middle, and sometimes deeply hollow beneath, running across the valve in about the line of the adductor plate of the fixed scutum: this ledge, in fact, marks and is partly caused by, the line of separation between the central or parietal, much modified, and the scarcely modified, upper or rim portion of the valve. The use of this ledge is apparently to give attachment, as does the under side of the adductor plate of the fixed scutum, to ligamentous fibres, presently to be mentioned, by which the shell is attached to the basal membrane: the carina and rostrum being so much more gently inclined, do not stand in need of a ledge for their attachment.

By comparing the moveable scutum and tergum with the corresponding fixed valves, in all the species, the modification of the latter may be clearly made out to have been effected as follows; and the case appears to me a striking and interesting one. The moveable scutum and tergum lie in the same plane, and are articulated by the means of three ridges on the tergum (including the occludent margin), and by two on the scutum. The fixed scutum and tergum have to be curved, and to be greatly increased in size; and this is brought about, as we shall see, by the large development of a certain small portion of each valve. Comparing first the moveable tergum (T) with the fixed tergum (T′), the umbo of growth matches the umbo of the four margins of the moveable valve, the carinal (_x_), basal (_z_), and occludent (_o_ in fig. 5), margins can be identified with certainty in the fixed valve, from their close similarity in shape, their absolute apposition, or correspondence in position. There remains only the scutal or articular margin, with its three articular ridges; of these, the uppermost (′), inasmuch as in most of the species it is hardly distinct from the occludent margin, can, as we have just seen, be clearly identified, and is overlapped, as it normally should be, by the upper tergal corner of the fixed scutum: the second or middle articular ridge, though not so distinct as in the moveable valves, can be plainly recognised (′′), T′, in fig. 1 _b_, and 5; and it serves its normal function of articulating the two valves together. But when we look in the fixed valve for the third or axial ridge (′′′), we find in its exact place, namely, extending from the umbo to the extreme opposite end of the valve, between the second articular ridge (′′) and the basal margin (_z_, see fig. 5), only that portion of the valve which I have called the parietal portion; consequently, I do not doubt that this really is the axial ridge largely expanded. So again in comparing the moveable scutum (S) with the fixed scutum (S′); two of the three margins of the former, namely, the occludent (_a_, see fig. 1 _b_) and basal (_b_), can be identified without a doubt in the fixed valve: the third and tergal margin remains; this should have two articular ridges; of these the upper one, still serving its normal function, can be detected in all the species (′ in fig. 1 _b_), and can be seen pretty plainly (′ fig. 5) in _V. nexa_: but of the lower and other articular ridge there is no sign,--excepting indeed the whole parietal portion of the valve, which, from holding an exactly homologous position with the lower articular ridge of the moveable valve, I cannot doubt in this ridge expanded and curiously metamorphosed. Hence, in both fixed scutum and tergum, it is the outermost or lowest of the articular ridges which has been modified and expanded, so as to rest on and be fixed to the surface of attachment. It would appear as if it had resulted from one ridge in each of these valves having been thus used up by expansion (so to express myself), that the suture between the fixed scutum and tergum is more simple than any other suture in the whole shell; and it is owing probably to this straightness, and consequent _tendency_ to weakness, that the valves do not grow along this line, and so do not become separated from each other during growth, as on the three other lines of suture. As it actually is, owing to this suture never being separated, it is even stronger than the others; its edges on the inside (fig. 1 _c_), I may add, are a little inflected or prominent.

_Rostrum_ and _Carina_: these valves differ from each other, only in the former (A) being rather the largest, and in being more plainly articulated with the fixed scutum, than is the carina (B) with the fixed tergum. Their umbones stand in their normal places, at the two ends of the orifice leading into the sack, that is, facing the dorso-ventral longitudinal plane of the animal; but they are very unequally developed on the two sides, and hence they rise very obliquely from the surface of attachment. Their summits are nearly square, which is caused by the continued growth on both sides of the oblique plates or ridges, by which they are articulated with the adjoining valves. These plates strikingly resemble, as already stated, the radii in certain species of Chthamalus. Without these articulating plates, the outline of the rostrum and carina would have been triangular, with the apex upwards. In _V. nexa_, in which the walls of the shell are almost perpendicular, the rostrum (A, fig. 5) is very peculiar and patelliformed, with the umbo sub-central: this results from the development of a border at the upper end of the valve. In this same species, the basal edges of the rostrum, carina, fixed scutum and tergum, are rectangularly inflected, so as to form a ledge round the basis, as in the case of some few species of Chthamalus,--the ledge appearing like part of the real basis. During the growth of the shell, the upper internal ends of the carina and rostrum are either rendered solid, or a ledge is formed on the inside across their summits, hollow beneath, like the sheath of the Balanidæ, to which solid or hollow ledge the basal margins of the moveable scutum and tergum are attached by a rim of membrane, forming a hinge.