A Monograph on the Sub-class Cirripedia (Volume 1 of 2)

Chapter C: VIRGATA, var. OLFERSII (6)

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The parasites of _S. vulgare_ take advantage of a pre-existing fold on the edge of the scutum, where the chitine border is thicker; and in this respect there is nothing different from what would naturally happen with an independent parasite; but in _S. ornatum_ the case is very different, for here the two scuta are specially modified, _before the attachment of the parasites_, in a manner which it is impossible to believe can be of any service to the species itself, irrespectively of the lodgment thus afforded for the males. So again in _S. rutilum_, the shape of the scutum seems adapted for the reception of the male, in a manner which must be attributed to its own growth, and not to the pressure or attachment of a foreign body. Now there is a strong and manifest improbability in an animal being specially modified to favour the parasitism of another, though there are innumerable instances in which parasites take advantage of pre-existing structures in the animals to which they are attached. On the other hand, there is no greater improbability in the female being modified for the attachment of the male, in a class in which all the individuals are attached to some object, than in the mutual organs of copulation being adapted to each other throughout the animal kingdom.

Generic Characters of the larval prehensile ANTENNÆ, in the Lepadidæ,
as far as known from their imperfect state of preservation, and the
number of species examined.

LEPAS: disc large, thin, almost _circular_, slightly elongated, with
several long spines on the hinder margin; end segment with three very
long, plumose spines on the upper _exterior_ angle.[61]

|_L. anatifera_ (?)
| |62
| | |--
| | | |20
| | | | |23
| | | | | |22
| | | | | | |--
| | | | | | | |--

|_L. australis_,
| |111
| | |--
| | | |40
| | | | |42
| | | | | |39
| | | | | | |18
| | | | | | | |30

|_L. pectinata_,
| |51
| | |--
| | | |23
| | | | |16
| | | | | |14
| | | | | | |9
| | | | | | | |16

|_L. fascicularis_,
| |60
| | |40
| | | |22
| | | | |16
| | | | | |15
| | | | | | |--
| | | | | | | |--

DICHELASPIS: disc _small_, thin, circular, with several spines on the
hinder margin; end segment, with two long spines on the upper _exterior_
angle.

|_D. Warwickii_,
| |54
| | |--
| | | |11
| | | | |7-8
| | | | | |7-8
| | | | | | |6
| | | | | | | |13-14

CONCHODERMA: disc large, thin, _transversely_ elongated, with several
long spines on the hinder margin; end segment, with two excessively
long, plumose spines on the upper _exterior_ corner.

|_C. virgata_,
| |82
| | |40
| | | |28
| | | | |25
| | | | | |35
| | | | | | |12
| | | | | | | |26

|_C. aurita._
| |--
| | |--
| | | |--
| | | | |28
| | | | | |40
| | | | | | |11
| | | | | | | |26

ALEPAS: disc small, slightly elongated, with two or more spines on the
hinder margin; end segment, with two long spines on the upper _inner_
corner, and four shorter ones on the exterior corner.

|_A. cornuta_,
| |60
| | |--
| | | |24
| | | | |14
| | | | | |12
| | | | | | |8
| | | | | | | |20

IBLA (parasitic males of): disc, _hoof-like_, _pointed_, elongated, with
a single spine on the hinder margin; end segment, with four short spines
on the upper exterior corner.

|_I. Cumingii_,
| |22
| | |--
| | | |7-8
| | | | |7
| | | | | |--
| | | | | | |3-4
| | | | | | | |7-8

|_I. quadrivalvis_,
| |32-33
| | |--
| | | |10
| | | | |8
| | | | | |5
| | | | | | |4
| | | | | | | |8

SCALPELLUM: disc _hoof-like_, generally _pointed_ and elongated, with a
single spine on the hinder margin; end segment, with a notch on the
inner[61] side, bearing two spines, longer than on the exterior corner.

|_S. vulgare_,
| |39
| | |19
| | | |10
| | | | |10-11
| | | | | |5-6
| | | | | | |6
| | | | | | | |7

|_S. ornatum_,
| |36
| | |21
| | | |10
| | | | |12
| | | | | |--
| | | | | | |--
| | | | | | | |--

|_S. Peronii_,
| |30
| | |19
| | | |--
| | | | |9
| | | | | |6
| | | | | | |5
| | | | | | | |10

POLLICIPES: disc small, _hoof-like_, not pointed, with a single spine on
the hinder margin; end segment, as in _Scalpellum_.

|_P. cornucopia_,
| |20
| | |--
| | | |6
| | | | |6
| | | | | |6
| | | | | | |6
| | | | | | | |8

[61] In the diameter of the disc, the thin membranous border,
which is present in the first three genera, is included; but I
have some doubts, whether this border be not the first rim of
cementing tissue, as all the specimens, of which measurements are
here given, had been removed after attachment. In using the terms
inner and outer sides of the end segment, it is supposed, that
this segment is stretched straight forwards, instead of being
bent rectangularly outwards, as in its natural position; and then
there can be no doubt which is the inner and outer sides.

It should be observed that the evidence in this summary is of a cumulative nature. If we think it highly, or in some degree probable,--from the ordinary form of _Ibla Cumingii_ having been shown on good evidence to be exclusively female,--from the absence of ova and ovaria in the assumed males of both species of Ibla, at the period when their vesiculæ seminales were gorged with spermatozoa,--from the close general resemblance between the parts of the mouth in the parasites and in the Iblas to which they are attached,--from the differences between the two parasites being strictly analogous to the differences between the two species of Ibla,--from the generic character of their prehensile antennæ,--and from other such points,--if from these several considerations, we admit that these parasites really are the males of the two species to which they adhere, then in some degree the occurrence of parasitic males in the allied genus Scalpellum is rendered more probable. So the absolute similarity in the antennæ of the males and hermaphrodites both in _S. vulgare_ and _S. Peronii_; and such relations as that of the relative villosity of the several species in this same genus, all in return strengthen the case in Ibla. Again, the six-valved parasites of _S. Peronii_ and _S. villosum_ are so closely similar, that their nature, whatever it may be, must be the same; hence we may add up the evidence derived from the identity of the antennæ in the parasite and hermaphrodite _S. Peronii_, with that from the antennæ in the male _S. villosum_, approaching in character to Pollicipes, to which genus the hermaphrodite is so closely allied; and to this evidence, again, may be added the singular coincident absence of caudal appendages in the male and hermaphrodite _S. villosum_. If these two six-valved parasites be received as the complemental males of their respective species, no one, probably, will doubt regarding the nature of the parasite of _S. rostratum_, in which the direct evidence is the weakest; but even in this case, the particular point of attachment, and the state of development of the valves, form a link connecting in some degree, the parasites of the first three species with the last two species of Scalpellum, in accordance with the affinities of the hermaphrodites.

When first examining the parasites of _S. rostratum_, _S. Peronii_, and _S. villosum_, before the weight of the cumulative evidence had struck me, and noting their apparent state of immaturity, it occurred to me that possibly they were the young of their respective species, in their normal state of development, attached to old individuals, as may often be seen in Lepas; this, however, would be a surprising fact, considering that _S. rostratum_ and _S. Peronii_ are ordinarily attached, in a certain definite position, to horny corallines, and considering that the exact points of attachment in these three parasites, (of which I have seen no other instance amongst common Cirripedes,) namely, between the scuta, would inevitably cause their early destruction, either directly or indirectly, by their living supports being destroyed. Nevertheless, I carefully examined a young specimen of _S. rostratum_ only thrice as large as the parasite; and not having very young specimens of _S. Peronii_ and _villosum_, I procured the young of closely-allied forms, namely, of _S. vulgare_, (with a capitulum only 4/100th of an inch in length,) and of _Pollicipes polymerus_, (with a capitulum of less size than that of one of the parasites,) and there was not the least sign of anything abnormal in the development of the valves. In _S. vulgare_, at a period when the calcified scuta could have been only 1/100th of an inch in length, (and therefore considerably less than the scuta in the parasites,) the upper latera must have been as much as 4/1000ths of an inch in length, and the valves of the lower whorl certainly distinguishable.

To sum up the evidence on the sex of the parasites, I was not able to discover a vestige of ova or ovaria in the two male Iblas; and I can venture to affirm positively, that the parasites of _S. Peronii_ and _S. villosum_ are not female. On the other hand, in the two male Iblas, I was enabled to demonstrate all the male organs, and I most distinctly saw spermatozoa. In the parasitic complemental male of _S. vulgare_, I also most plainly saw spermatozoa. In the parasites of _S. rostratum_, _S. Peronii_, and _S. villosum_, the external male organs were present. I may here just allude to the facts given in detail under Ibla, showing that it was hardly possible that I could be mistaken regarding the exclusively female sex of the ordinary form of _I. Cumingii_, seeing how immediately I perceived all the male organs in the hermaphrodite _I. quadrivalvis_; and as the parasite contained spermatozoa and no ova, the only possible way to escape from the conclusion that it was the male and _I. Cumingii_ the female of the same species, was to invent two hypothetical creatures, of opposite sexes to the Ibla and its parasite, and which, though Cirripedes, would have to be locomotive! I insisted upon this alternative, because if the parasite of _I. Cumingii_ be the male of that species, then unquestionably we have in _I. quadrivalvis_ a male, complemental to an hermaphrodite,--a conclusion, as we have seen, hardly to be avoided in the genus Scalpellum, even if we trust exclusively to the facts therein exhibited.

With respect to the positions of the parasitic males, in relation to the impregnation of the ova in the females and hermaphrodites, it may be observed that in the two male Iblas, the elongated moveable body seems perfectly adapted for this end; in the males of the first three species of Scalpellum, the spermatozoa, owing to the manner in which the thorax is bent when protruded, would be easily discharged into the sack of the female or hermaphrodite; this would likewise probably happen with the complemental male of _S. rostratum_, considering its position within the orifice of the capitulum, between the mouth and the adductor scutorum muscle. The males of _S. Peronii_ and _villosum_ being fixed a little way beneath the orifice of the sack, below the adductor muscle, are less favorably situated, but the spermatozoa would probably be drawn into the sack by the ordinary action of the cirri of the hermaphrodite, and therefore would at least have as good a chance of fertilising some of the ova, as the pollen of many dioecious plants, trusted to the wind, has of reaching the stigmas of the female plants. Regarding the final cause, both of the simpler case of the separation of the sexes, notwithstanding that the two individuals, after the metamorphosis of the male, become indissolubly united together, and of the much more singular fact of the existence of Complemental males, I can throw no light; I will only repeat the observation made more than once, that in some of the hermaphrodites, the vesiculæ seminales were small, and that in others the probosciformed penis was unusually short and thin.

Viewing the parasitic males, in relation to the structure and appearance of the species to which they belong, they present a singular series. In _S. Peronii_ and _S. villosum_, the internal organs have the appearance of immaturity; the shape of the capitulum is specially modified for its reception between the scuta of the hermaphrodite, and several of the valves have not been developed. This atrophy of the valves, is carried much further in _S. rostratum_. In Ibla, many of the parts are embryonic in character, but others mature and perfect; some parts, as the capitulum, thorax, and cirri, are in a quite extraordinary state of atrophy; in fact, the parasitic males of Ibla consist almost exclusively of a mouth, mounted on the summit of the three anterior segments of the 21 normal segments of the archetype crustacean. In the males of the first three species of Scalpellum, some of the characters are embryonic,--as the absence of a mouth, the presence of the abdominal lobe, and the position of the few existing internal organs; other characters, such as the general external form, the four bead-like valves, the narrow orifice, the peculiar thorax and limbs, are special developments. These three latter parasites, certainly, are wonderfully unlike the hermaphrodites or females to which they belong; if classed as independent animals, they would assuredly be placed not in another family, but in another Order. When mature they may be said essentially to be mere bags of spermatozoa.

In looking for analogies to the facts here described, I have already referred to the minute male Lerneidæ which cling to their females,--to the worm-like males of certain Cephalopoda, parasitic on the females,--and to certain Entozoons, in which the sexes cohere, or even are organically blended by one extremity of their bodies. The females in certain insects depart in structure, nearly or quite as widely from the Order to which they belong, as do these male parasitic Cirripedes; some of these females, like the males of the first three species of Scalpellum, do not feed, and some, I believe, have their mouths in a rudimentary condition; but in this latter respect, we have, amongst the Rotifera, a closely analogous case in the male of the Asplanchna of Gosse, which was discovered by Mr. Brightwell[62] to be entirely destitute of mouth and stomach, exactly as I find to be the case with the parasitic male of _S. vulgare_, and doubtless with its two close allies. For any analogy to the existence of males, complemental to hermaphrodites, we must look to the vegetable kingdom.

Finally, the simple fact of the diversity in the sexual relations, displayed within the limits of the general Ibla and Scalpellum, appears to me eminently curious; we have (1st) a female, with a male (or rarely two) permanently attached to her, protected by her, and nourished by any minute animals which may enter her sack; (2d) a female, with successive pairs of short-lived males, destitute of mouth and stomach, inhabiting two pouches formed on the under sides of her valves; (3d) an hermaphrodite, with from one or two, up to five or six similar short-lived males without mouth or stomach, attached to one particular spot on each side of the orifice of the capitulum; and (4th) hermaphrodites, with occasionally one, two, or three males, capable of seizing and devouring their prey in the ordinary Cirripedial method, attached to two different parts of the capitulum, in both cases being protected by the closing of the scuta. As I am summing up the singularity of the phenomena here presented, I will allude to the marvellous assemblage of beings seen by me within the sack of an _Ibla quadrivalvis_,--namely, an old and young male, both minute, worm-like, destitute of a capitulum, with a great mouth, and rudimentary thorax and limbs, attached to each other and to the hermaphrodite, which latter is utterly different in appearance and structure; secondly, the four or five, free, boat-shaped larvæ, with their curious prehensile antennæ, two great compound eyes, no mouth, and six natatory legs; and lastly, several hundreds of the larvæ in their first stage of development, globular, with horn-shaped projections on their carapaces, minute single eyes, filiformed antennæ, probosciformed mouths, and only three pair of natatory legs; what diverse beings, with scarcely anything in common, and yet all belonging to the same species!

[62] ‘Annals of Natural History,’ vol. ii, (2d series, 1848,) p.
153, Pl. vi. Mr. Dalrymple has published a very interesting paper
on the same subject in the ‘Philosophical Transactions,’ (p.
342,) 1849; and there is another Memoir by Mr. Gosse in the
‘Annals of Natural History,’ vol. vi, (1850,) p. 18.

_Genus_--POLLICIPES. Pl. VII.

POLLICIES. _Leach._ Journal de Physique, tom. lxxxv, Julius,
1817.[63]

LEPAS. _Linn._ Systema Naturæ, 1767.

ANATIFA. _Brugière._ Encyclop. Méthod. (des Vers), 1789.

MITELLA. _Oken._ Lehrbuch der Naturgeschichte, 1815.

RAMPHIDIONA. _Schumacher._ Essai d’un Nouveau Syst. &c., 1817
(ante Julium).

POLYLEPAS. _De Blainville._ Dict. des Sc. Nat., 1824.

CAPITULUM (secundum Klein). _J. E. Gray._ Annals of Philos., tom.
x, new series, Aug. 1825.

[63] This is one of the rare cases in which, after much
deliberation, and with the advice of several distinguished
naturalists, I have departed from the Rules of the British
Association; for it will be seen that _Mitella_ of Oken, and
_Ramphidiona_ of Schumacher, are both prior to _Pollicipes_ of
Leach; yet, as the latter name has been universally adopted
throughout Europe and North America, and has been extensively
used in geological works, it appears to me to be as useless as
hopeless to attempt any change. It may be observed that the genus
_Pollicipes_ was originally proposed by Sir John Hill (‘History
of Animals,’ vol. iii, p. 170), in 1752, but as this was before
the discovery of the binomial system, by the Rules it is
absolutely excluded as of any authority. In my opinion, under all
these circumstances, it would be mere pedantry to go back to
Oken’s ‘Lehrbuch der Naturgeschichte’ for the name _Mitella_,--a
work little known, and displaying entire ignorance regarding the
Cirripedia.

_Valvæ ab 18 usque ad 100 et amplius: lateribus verticilli inferioris multis; lineis incrementi deorsùm ordinatis: sub-rostrum semper adest: pedunculus squamiferus._

Valves from 18 to above 100 in number: latera of the lower whorl numerous, with their lines of growth directed downwards: sub-rostrum always present: peduncle squamiferous.

Hermaphrodite; filamentary appendages either none, or numerous and seated on the prosoma and at the bases of the first pair of cirri; labrum bullate; trophi various; olfactory orifices generally highly prominent; caudal appendages uni-articulate and spinose, or multi-articulate.

Attached to fixed, or less commonly to floating objects, in the
warmer temperate, and tropical seas.

It has been remarked, under Scalpellum, how imperfectly that genus is separated from Pollicipes; and we have seen under _Scalpellum villosum_ that the addition of a few small valves to the lower whorl, would convert it into a Pollicipes, most closely allied to _P. sertus_ and _spinosus_. It has also been shown, that the six recent species of Pollicipes might be divided into three genera, of which _P. cornucopia_, _P. elegans_, and _P. polymerus_, would form one thoroughly natural genus, as natural as Lepas and the earlier genera; _P. mitella_ would form a second; and _P. sertus_ and _P. spinosus_ a third; but I have acted to the best of my judgment in at present retaining the six species together. As far as the valves of the capitulum are concerned, it would be very difficult to separate _P. mitella_ from _P. sertus_ and _spinosus_.

_Description._ The number of valves in the capitulum has in this genus acquired its maximum. The number varies considerably in the same species, and even on opposite sides of the same individual, and generally increases with age. It is more important, that the number of the whorls in _P. cornucopia_, and in the two following closely-allied forms, also increases with age. In _P. sertus_ and _P. spinosus_, even the number of the whorls varies in different individuals, independently of age. The valves are arranged alternately with those above and below; they are generally thick and strong, making the capitulum somewhat massive; in some species they are subject to much disintegration; but in others, the apices of the several valves, especially of the carina and rostrum, are well preserved, and project freely: they are covered with membrane, which, differently from in most species of Scalpellum, either does not bear any spines, or only exceedingly minute points. In all the species there is a sub-rostrum and sub-carina, and often beneath these a second sub-rostrum and sub-carina. In medium-sized specimens there are at least 20 valves in the lowermost whorl. The carina is either straight or curved, but never rectangularly bent, and is always of considerable breadth. None of the valves are added to at their upper ends. The scuta have a deep pit for the adductor muscle. The valves lie either some little way apart, or more commonly close together. In _P. mitella_ the scuta and terga are locked together by a fold, and the valves of the lower whorl overlap each other in a peculiar manner, resembling that in which the compartments in the shells of Sessile Cirripedes fold over each other.

The _Peduncle_ is of considerable length in some of the species, and rather short in others; it is, in every case, clothed with calcified scales. The scales in the first four species are placed alternately and symmetrically; they are formed and added to in the same manner as in Scalpellum; they differ in size according to the size of the individual, and consequently the lower scales on the peduncle, formed when the specimen was young, are smaller than the upper scales; the lower scales are separated from each other by wide interspaces of membrane, owing to the continued growth of the peduncle by the formation of new layers of membrane, and the disintegration of the old outer layers. Each scale is invested by tough membrane (or has been, for it is often abraded off), in the same manner as the valves; each is furnished with one or more tubuli, in connection with the underlying corium. In _P. sertus_ and _P. spinosus_, the scales are small, spindle-shaped, and not of equal sizes, and the rows are distant from each other, so that their alternate arrangement is not distinguishable; in these two species, new scales are formed round the summit of the peduncle, and the growth of each is completed whilst remaining in the uppermost row; but, besides these normal scales, such as exist in the other species of Pollicipes and in Scalpellum, new scales are formed in the lower part of the peduncle, which are generally of very irregular shapes, are often larger than the upper ones, are crowded together, and sometimes do not reach the outer surface of the membrane. This formation of scales in the lower part of the peduncle, independently of the regular rows round the uppermost part, is perhaps a feeble representation of the calcareous cup at the bottom of the peduncle in the genus Lithotrya. The prehensile antennæ will be described under _P. cornucopia_.

_Size._--Most of the species are large: and _P. mitella_ is the most massive of the Pedunculated Cirripedes.

The _Mouth_ is not placed far from the adductor muscle. The labrum is highly bullate. The mandibles have either three or four main teeth (Pl. X, fig. 1), with often either one or two smaller teeth inserted between the first and second. The maxillæ (Pl. X, figs. 13, 14), have their edges either straight and square, or notched, or more commonly with two or three prominences bearing tufts of finer spines. The outer maxillæ (fig. 17) generally have a deep notch on their inner edges, but this is not invariable. The olfactory orifices in most of the species are highly prominent.

_Cirri._--The first pair is never placed far distant from the second. The posterior cirri have strong, somewhat protuberant segments; and between each of the four or five pair of main spines (Pl. X, fig. 27), there is a rather large tuft of straight, fine, short bristles. The second and third pair have the basal segments, either of the anterior rami, or of both rami, so thickly clothed with spines (fig. 25), as to be brush-like: in _P. mitella_, however, the third pair is like the three posterior pair in the arrangement of its spines, in this respect resembling the sessile Chthamalinæ. The caudal appendages are either uni-articulate and spinose, or multi-articulate: it is remarkable that there should be this difference in such closely allied species as _P. cornucopia_ and _P. polymerus_: the short, obtuse, obscurely-articulated caudal appendage of the former species (fig. 22) makes an excellent passage from the uni-articulate (fig. 19) to the multi-articulate form, as in _P. mitella_.

The stomach, in those species which I opened, is destitute of cæca; the hepatic glands are arranged in straight lines; the rectum is unusually short. The prosoma is well developed.

In _P. cornucopia_, _P. elegans_, and _P. polymerus_, there are numerous filamentary appendages both on the prosoma, and at the bases of the first pair of cirri: these appendages are occupied by testes, and I suspect stand in relation to the length of the peduncle and consequent great development of the ovaria. In order to give space for the filamentary appendages, the sack (generally roughened by small inwardly-pointing papillæ) penetrates more deeply than usual into the upper part of the peduncle. There are small ovigerous fræna in _P. sertus_, _P. spinosus_, and _P. mitella_: in the three other species, the frænum or fold occupies the usual position on each side, and is large; but in one specimen carefully examined by me, I was unable to see any glands; and in another specimen, the ovigerous lamellæ were not attached to the fræna; hence I conclude that the fræna are functionless in these three species.

_Affinities._--I have already remarked on the close relationship between this genus and Scalpellum; there is also some affinity with Lithotrya.

_Distribution._--All over the world. The _P. cornucopia_ ranges
from Scotland to Teneriffe: the _P. polymerus_ is found in
opposite hemispheres in the Pacific Ocean, extending from
California to at least as far as 32° south of the Equator.

_Geological History._--Having so lately given, in the ‘Memoirs of the Palæontographical Society,’ a full account of all the fossil species known, I will not repeat here the conclusions there arrived at. I will only state, that species of Pollicipes are found in all the formations, extending from the Lower Oolite to the Upper Tertiary beds.

1. POLLICIPES CORNUCOPIA. Pl. VII, fig. 1.

POLLICIPES CORNUCOPIA. _Leach._ Encyclop. Brit. Supp., vol. iii,
1824.

---- SMYTHII, var. _Leach_. Ibid.

LEPAS POLLICIPES. _Gmelin._ Systema Naturæ, 1789.

---- GALLORUM. _Spengler._ Skrivter Naturhist. Selskabet, Bd. i,
Tab. vi, fig. 9, 1790.

_P. capitulo, valvarum duobus aut pluribus sub-rostro verticillis instructo: valvis albis, aut glaucis: pedunculo, squamarum densis verticillis symmetricè dispositis._

Capitulum with two or more whorls of valves under the rostrum; valves white or gray; scales on the peduncle symmetrically arranged in close whorls.

Maxillæ with three tufts of fine bristles, separated by larger spines: segments in the first cirrus less than half the number of those in the sixth cirrus: caudal appendages multi-articulate: filamentary appendages attached to the prosoma.

Coast of Portugal; mouth of the Tagus. England,[64] Ireland, and
the Frith of Forth in Scotland. Mediterranean (according to
Brugière): Teneriffe: Mogador, Africa.

[64] This species is said by Montagu (‘Test. Brit. Supplement’)
to have been found attached to drift timber in the Frith of
Forth, and to the bottom of a wrecked vessel towed into
Dartmouth. According to Mr. W. Thompson (‘Annals of Nat. Hist.’
vol. xiii, p. 436), it has been found attached to wood-work near
Dublin.

Capitulum, obtusely triangular, massive: valves close together, rather thick, with their exterior surfaces convex, naked, except in the lower parts, where united together by tough, greenish-brown membrane, destitute of spines. The edges of the orifice are widely bordered by membrane, coloured fine crimson red. The valves, in a specimen with a capitulum above three quarters of an inch long, were 52 in number; in a specimen one fifth of an inch long, only between 20 and 30. Two whorls of valves are distinct beneath the carina and rostrum. In one specimen in Mr. Cuming’s collection, with a capitulum 1.4 of an inch long, there were three whorls beneath the rostrum, and four beneath the carina. The scuta, terga, and carina are much larger than the other valves.

_Scuta_, oval, the basal and tergo-lateral margins sweeping into each other, and the apex pointed; internally (Pl. VII, fig. 1 _a_) the pit for the adductor muscle is deep.

_Terga_, larger than the scuta, internally (fig. 1 _a_) slightly concave; carinal margin much curved and protuberant; basal angle blunt; scutal margin either curved with the upper part straight, or formed of two almost distinct lines, corresponding with the tergal margin of the scutum, and with one of the sides of the upper latus.

_Carina_, much curved, extending far up between the terga, internally deeply concave, widening much from the top to the bottom; basal margin highly protuberant, with a central portion either truncated and very slightly hollowed out, or bluntly and rectangularly pointed, with the apex itself rounded.

_Rostrum_, not one third of the length of the carina, concave, triangular, with the basal margin slightly protuberant. Of the other valves, including the sub-carina and sub-rostrum, the shape of their inner surfaces is sub-triangular, with the basal margin convex; externally the umbones are pointed, and slightly curled inwards, so as to overlap each other like tiles: the smaller valves, however, of the lower whorls (fig. 1 _a_) are more or less transversely elongated, so as to become almost elliptic instead of triangular. Of the latera, the upper pair, which corresponds to the interspace between the scuta and terga, is the largest, but barely exceeds in size the pair answering to the carinal latera in Scalpellum, which lie between the terga and carina: the next largest pair is the rostral, or that between the scuta and rostrum. Some, however, of the lower latera are of nearly equal size.

_Peduncle_, narrower, but generally longer than the capitulum; upper part encased with small calcareous scales, with their apices curved inwards, and overlapping each other. The inner surface of each scale is triangular, with the basal margin protuberant. The scales continue to grow or be added to, only in about the ten upper whorls, which form but a small part of the whole peduncle; in the lower part, the scales become further and further separated from each other. The surface of attachment, in full-grown specimens, is broad; but in two very young specimens, which I removed with great care after the action of potash, I found the peduncle ending in a filiform prolongation, such as often occurs in _Scalpellum vulgare_ and in _Lepas fascicularis_. At the extremity of the pointed peduncle, there were seated the larval prehensile antennæ, of which the following measurements are given to show how minute they are.

_Inch._
Length, from apex of disc, to the further
edge of the basal articulation 20/6000
Breadth of basal segment, in broadest part 6/6000
Hoof-like disc, length of 6/6000
Ultimate segment, entire length of 6/6000
“ “ breadth, in broadest part 6/20000

The disc resembles a broad, rounded hoof, very little longer than broad, and narrowed in at the heel; the apex is not at all pointed, and bears some minute and thin spines. There is one large spine on the under side of the disc; and another on the basal segment, on the outside, in the usual position. The ultimate segment is long and thin; it has a notch on the inner side (the segment supposed to be stretched forward), bearing two or three long flexuous spines; and there are three or four other spines on the summit: altogether there is a close resemblance with the antennæ in Scalpellum, excepting that the hoof-like disc is not here pointed.

_Colours._--Valves internally tinted, in parts, grey; peduncle, brown; corium of sack, purplish-brown, of peduncle, rich coppery brown; cirri, banded dorsally, and with the front surfaces of the segments, purplish-brown. Edge of the orifice of sack, fine crimson red. The specimen here described had been dried for a few weeks, and was then moistened.

_Dimensions._--The largest specimen which I have seen, in Mr. Cuming’s collection, had a capitulum 1 and 4/10ths of an inch long; a fine specimen, from Teneriffe, was 9/10ths in length. In a specimen with a capitulum 1/20th of an inch long, and about the same in breadth, there were eighteen valves; so that, besides the principal valves, five pair of latera, the sub-carina, and sub-rostrum, were already developed, and on the upper part of the peduncle, there were many calcareous scales.

_Filamentary Appendages._--The prosoma is well-developed, with thirteen or fourteen pair of short, blunt filaments, placed close together in two longitudinal rows; those nearest the thorax are the longest; outside this double row, on each side, there is a row of papillæ, indicating a tendency to the formation of two other rows of filaments. There is a pair of longer filaments, one on each side of the mouth, pointing upwards, and thinly clothed with long spines; at the bases of the first pair of cirri there is a second pair of filaments, shorter and bearing a few minute spines. The bottom of the sack is studded with small rounded papillæ, with roughened summits.

_Mouth_, not placed very far from the adductor muscle.

_Labrum_, highly bullate, equalling, in its longitudinal diameter, the rest of the mouth; upper part square, not overhanging the lower part; there are some small teeth on the crest.

_Palpi_, oval, outer and inner margins nearly alike, thickly clothed with spines.

_Mandibles_, with three very strong, yellow teeth; inferior point broad, coarsely pectinated. In one specimen, on one side, the third tooth was represented by two smaller teeth.

The _Maxillæ_ bear three conspicuous tufts of fine bristles, separated by larger spines; the first tuft is placed close to the two, upper, large, but unequally-sized spines; the second tuft is placed in the middle, and the third at the inferior angle. The two latter tufts stand on prominences; between the two upper tufts there are three pair, and between the two lower tufts four or more pair of rather strong spines: (see the figure, 13, Pl. X, in the allied _P. polymerus_.)

_Outer Maxillæ_, with the inner edge divided in the middle by a conspicuous notch, and with the bristles above and below short, making two _equal_ combs. On the exterior surface, the bristles are longer and more spread out. Olfactory orifices prominent, protected by a punctured swelling between the bases of the first pair of cirri.

_Cirri_, short and rather thick; the first pair is not far removed from the second. The segments of the three posterior pair are somewhat protuberant, bearing six pair of short, strong spines, graduated in length, between which there is a very thick, longitudinal brush of short, fine, straight bristles, of which the lower ones are the longest; some thick, minute spines arise from the upper lateral edges of the segments. The spines in the dorsal tufts are short, much crowded, and of nearly equal length; see figure, 27, Pl. X, in the allied _P. polymerus_. In a specimen in which the sixth cirrus had seventeen segments, the first cirrus had, in the shorter ramus, eight segments, of which the lower four were thick and protuberant, with the spines doubly serrated. In this same specimen, the anterior ramus of the second cirrus had twelve segments, of which the five basal ones were highly protuberant, and thickly clothed with non-serrated spines. In the third cirrus the basal segments of the anterior ramus are highly protuberant. The basal segments in the posterior rami of both these cirri, are slightly protuberant, but otherwise resemble the segments in the three posterior pair.

The _Caudal Appendages_ (Pl. X, fig. 22), in full-grown specimens, just exceed in length the lower segments of the pedicels of the sixth cirrus; they are nearly cylindrical, bluntly pointed, with five oblique imperfect articulations; the lower or basal articulations cannot be traced all round, being distinct only on the ventral surface. There is a row of short spines round the upper edge of each segment, with a little, short tuft on the point of the terminal segment. In a rather young specimen, however, with its capitulum one fifth of an inch long, each appendage certainly consisted of a single segment, with spines only on the summit.

_Penis_ purple, with excessively short and fine spines in tufts, chiefly near the extremity. In a specimen with a capitulum only one fifth of an inch long, the penis consisted of a mere pointed papilla, not so long as the caudal appendage, and therefore equalling in length only the lower segment of the pedicel of the sixth cirrus.

_Ovigerous fræna._--I could see none, though there were two large lamellæ in the sack. The ova were flesh-coloured, but they had been dried and then placed in spirits. The ova were wonderfully numerous, oval, much elongated, and 1/100th of an inch in length.

2. POLLICIPES ELEGANS.

POLLICIPES ELEGANS. _Lesson._ Voyage de la Coquille, tom. ii, p.
441, 1830, et Illust. Zool., Pl. xxxix, 1831.

---- RUBER. _G. B. Sowerby._ Zoolog. Proc., 1833, p. 74.

_P. capitulo, valvarum duobus aut pluribus sub-rostro verticillis instructo: valvis et pedunculi squamis rufo-aurantiacis: squamarum verticillis densis symmetricè dispositis._

Capitulum with two or more whorls of valves under the rostrum: valves and scales of peduncle reddish-orange; the latter symmetrically arranged in close whorls.

Maxillæ with three tufts of fine bristles, separated by larger spines; segments is in the first cirrus more than half the number of those in the sixth cirrus; caudal appendages multi-articulate; filamentary appendages attached to the prosoma.

Coast of Peru, Payta, attached to wooden posts, according to
Lesson: Lobos Island, Peru, Mus. Cuming: West Coast of Mexico,
Tehuantepec, on an exposed rock, according to Hinds.

The resemblance of this species is so close to _P. cornucopia_, that it is quite useless to do more than point out the few points of difference. Valves of the capitulum and scales of the peduncle, coloured (after having been in spirits,) reddish-orange. In a specimen in which the capitulum was 1.3 of an inch in length, there were three whorls of valves below the carina; in this large specimen altogether there were about eighty valves; in medium-sized specimens, the number is about the same as in _P. cornucopia_. The upper latus, (viewed internally,) has an area about twice as large as that latus, which corresponds to the interspace between the carina and terga; whereas in _P. cornucopia_ the upper latus is only slightly larger than this same valve. The apex of the basal internal margin of the carina is here rounded, instead of being square, as is generally the case with _P. cornucopia_. The strong membranous margin of the orifice of the sack, in its upper part, is almost one third as wide as the widest part of the terga, whereas in _P. cornucopia_ it is only one fourth of this same width. The peduncle apparently is rather longer, compared with _P. cornucopia_, and the calcareous scales on it perhaps a little larger in proportion.

In a very young specimen, with the capitulum barely exceeding 1/20th of an inch in length, I could distinguish the sub-rostrum, sub-carina, the upper, and some of the lower latera.

_Filamentary Appendages._--These, in a medium-sized specimen, are arranged on the prosoma in four longitudinal approximate rows, there being twelve in each row; those in the two outer rows are only half the length of those in the two inner rows; those nearest the thorax are the longest; there are some papillæ outside the outer rows. In a very large specimen with its capitulum 1.3 in length, these filaments were very much more numerous, and some were placed on the first segment of the thorax, and at the bases of several of the posterior cirri. Some of the filaments are bifid, trifid, and even branched. In all the specimens, at the bases of the first pair of cirri, there are, on each side, a pair of filaments, (one below the other,) pointing upwards, less than half as long as those on the prosoma: also on each side of the mouth, there is a longer and thicker filament, pointing upwards, with a few very minute scattered spines on it; the apices of these three pair of filaments, as well as of some of the others, are roughened with very minute pectinated scales. All these filaments were gorged with the branching testes.

_Mouth._--The parts are closely similar to those in _P. cornucopia_; in the mandibles, the interspace between the third tooth and the inferior angle, is slightly pectinated: in the maxillæ, there are six or eight pairs of spines between the two upper tufts of fine spines.

_Cirri._--These are in most respects similar, to those of _P. cornucopia_. In a specimen in which the sixth cirrus had eighteen segments, the shorter ramus of the first pair had ten segments, of which the five lower segments were thick and clothed with doubly serrated spines. In the second cirrus the anterior ramus had fifteen segments, of which the four basal ones were highly protuberant, and thickly clothed with spines. These spines, and some on the third cirrus, and a few on the first cirrus, have peculiar bent teeth, presently to be described under _P. polymerus_. These singularly toothed spines are absent in _P. cornucopia_. From the above numbers, we see that the first and second pairs of cirri have more segments in proportion to the sixth pair, than in _P. cornucopia_; and in the second pair, a fewer proportional number of the basal segments are protuberant and thickly clothed with spines.

_Caudal Appendages_, shorter than the lower segments of the pedicels of the sixth cirrus, with only four articulations; rather constricted near the base.

The _Ovigerous Fræna_ consist of very long and prominent folds, thinning out to nothing towards the bases of the scuta, but not furnished, as far as I could see, with glands, and therefore not normally functional.

_Diagnosis with P. cornucopia._--The reddish-orange colour of the valves alone suffices. There is a very slight difference, in the larger proportional size of the upper latera, and in the outline of the basal margin of the carina. In the maxillæ there is, in _P. elegans_, a greater width between the two upper tufts of fine spines. In the cirri, the segments in the first pair, are more than half as many as those in the sixth pair; in the anterior ramus of the second pair, only 4/15ths of the segments are protuberant and brush-like, whereas in _P. cornucopia_ 5/12ths are in this condition.

3. POLLICIPES POLYMERUS. Pl. VII, fig. 2.

POLLICIPES POLYMERUS.(!) _G.B. Sowerby._ Proc. Zool. Soc., 1833,
p. 74.

--MORTONI. (!) _Conrad._ Journal Acad. Nat. Sci. Philadelphia,
vol. vii, p. 261, Pl. xx, fig. 12, 1837.

_P. capitulo, valvarum duobus, tribus, aut pluribus sub-rostro verticillis instructo: valvis sub-fuscis: lateribus à supremo ad infimum gradatim quoad magnitudinem positis: carinæ margine basali (introrsùm spectanti) ad medium excavato: pedunculi squamarum verticillis densis, symmetricè dispositis._

Capitulum with two, three, or more whorls of valves under the rostrum: valves brownish: latera regularly graduated in size from the uppermost to the lowest: carina with the basal margin, (viewed internally,) hollowed out in the middle: scales of the peduncle symmetrically arranged in close whorls.

Maxillæ with three tufts of fine bristles, separated by larger spines; caudal appendages uniarticulate; filamentary appendages attached to the prosoma.

Upper California, St. Diego and Barbara, 32° to 35° N.,
according to Conrad; Mus. Cuming: Low Archipelago, Pacific
Ocean; Mus. Coll. of Surgeons: Southern Pacific Ocean, collected
during the Antarctic Expedition, Mus. Brit.

_Capitulum_, but little compressed, broad, with the scuta and terga placed in a more oblique direction, with respect to the peduncle, than is usual, so that the line of orifice forms an unusually small angle with the basal margin of the capitulum. The capitulum is composed of several whorls of valves, which gradually decrease in size from above downwards. In a medium-sized specimen there were four whorls under the rostrum; in the lowest of these whorls, there were between eighty and ninety valves, and in the whole capitulum from one hundred and seventy, to one hundred and eighty. The valves in the lower whorls are not of equal sizes. Viewed externally, the valves seem to touch and overlap each other; viewed internally (Pl. VII, fig. 2 _a_) they are found to be just separated from each other by transparent membrane; none of the valves are articulated together. The outer surfaces of nearly all the valves, except in the two last formed whorls, are much disintegrated, and seem to be composed of alternate white and brown layers of shell. The membrane connecting the valves, as well as that of the peduncle, (in specimens long kept in spirits,) is brown; but in some dried specimens, there are indications of its having been coloured crimson (as in _P. cornucopia_), round the orifice and between the valves.

_Scuta_, irregularly oval, convex, narrow at the upper end; basal margin may be almost said to be formed of three short, unequal margins, corresponding with the rostrum, the rostral and the adjoining latus. The edge corresponding with the latter, is the best marked, and is generally slightly hollowed out, as if a piece had been broken off. The tergo-lateral margin is curved and protuberant. The umbo projects a little over the scutal margin of the terga.

_Terga_, projecting beyond the other valves to an unusually small degree, broadly oval; basal angle bluntly pointed, apex rounded, blunt; scutal margin, hollowed out to receive the upper part of the tergal margin of the scuta; carinal margin curved and protuberant; occludent margin consists of two short sides at right angles to each other. The whole valve in length and area is about equal to the scuta; internally, somewhat concave.

_Carina_, triangular, rather narrow, internally deeply concave, very slightly curled inwards; basal margin protuberant, with a large central portion considerably hollowed out.

_Rostrum_, triangular, of nearly the same shape as the carina, but only one third of its length, internally very slightly concave, and with the basal margin various, being either truncated or angularly prominent in the middle.

_Latera._--The upper pair (corresponding to the interval between the scuta and terga) is only a trifle larger than the latera immediately beneath; and these only a little larger than those lower down. In the lowest whorl, the valves are very minute, though still about twice as large as the scales on the peduncle, and of a different shape from them. The upper latera (viewed internally) are almost diamond-shaped, owing to the prominence of the basal margin, but this varies considerably in degree. The latera in the next whorl are triangular, with the basal margins protuberant and arched, in a less and less degree in the lower whorls, until in the lowest, the valves are elongated transversely.

_Microscopical Structure._--A valve placed in acid leaves a thick opaque mass, formed of three different kinds of tissue, one having a finely shaded appearance; a second with a largely hexagonal reticulated structure, and the third thin, transparent, and marked with arborescent lines, which I imagine to be tubes, as will be hereafter seen in Lithotrya. Near the exterior surface, there are many tubuli. It appears to me probable that the strong tendency which the valves in this species have to disintegrate, is connected with the unusual quantity of animalized tissue contained by them. Externally the valves are covered by a strong membrane, either white or yellow, or white streaked with yellow, and marked by lines of growth, and by longitudinal, sinuous, little ridges.

_Peduncle_, in the upper part, of rather less diameter than the capitulum; twice or thrice as long as it; tapering a little downwards; surface of attachment wide and flat. Calcareous scales, minute, symmetrically and closely packed together: each scale is much flattened, and its shape, including the imbedded portion, is that of a spear with its point broken off. The basal end of each scale is conically hollow, and from the layers of growth conforming to this hollow, there is a false _appearance_ of an open tube running through the scale.

_Attachment._--The surface of attachment is wide: the two cement-ducts, after running down the sides of the peduncle in a sinuous course, within the longitudinal muscles and close outside the ovarian tubes, pass through the corium, and then separately form the most abrupt loops or folds. These are represented in Pl. IX, fig. 2, in which a space about 1/10th of an inch square is given, as seen from the outside. At each of the bends, an aperture has been formed through the membrane of the peduncle, and cement poured forth. The manner in which the discs of cement (_b_) come out of the two ducts (_a_ _a_), and reach the external surface, is shown in the section, figure 2 _a´_. The two tubes are firmly attached to the older layers of membrane, and are covered by the last-formed layers. In a young specimen, the cement-ducts were a little above 2/2000ths of an inch in diameter, which had increased, in a medium-sized specimen, to 5/2000. The cement-glands are retort-shaped, seated near each other, high up in the peduncle.

_Size._--The largest specimen which I have seen, was three inches in length including the peduncle; the capitulum was 9/10ths of an inch long, and one in width.

_Young Specimen._--I examined one with a capitulum 18/1000ths of an inch long, measured from the lowest whorl to the tips of the terga; the width was only 13/1000ths of an inch; in old specimens the width of the capitulum is greater than the length. The length of one of the scuta was 14/1000ths of an inch, therefore, greater than the width of the entire capitulum, which is not the case with mature specimens. Besides the scuta and terga, the carina and rostrum, and three pair of large latera, there was a lower whorl formed of ten or twelve valves, giving altogether to the capitulum of this very small specimen, either twenty-two or twenty-four valves.

_Shape of Body, Sack, Colours, &c._--From the position of the orifice of the capitulum, the animal’s body is suspended to the scuta in a more transverse direction than is usual. The prosoma is well-developed, and is distinctly separated from the three posterior thoracic segments, by a band of thin membrane. The tunic of the basal part of the sack, where it enters the peduncle in a blunt point, is thickened and covered with roughened rounded papillæ. The corium of the sack under the valves, is coloured (after spirits) so dark a brown as to be nearly black; the cirri and trophi are similar, but with a tinge of greenish-purple.

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A Monograph on the Sub-class Cirripedia (Volume 1 of 2)Chapter C: VIRGATA, var. OLFERSII (6)

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