VERRUCA PRISCA. Bosquet. Monographie des Crustacés fossiles du Terrain Crét. de Limbourg, Tab. 1, fig. 1-6; 1853.
Shell smooth: moveable scutum, with the lower articular ridge somewhat broader than the upper articular ridge.
Fossil—‘Système Senonien et Maestrichtien,’ Belgium, Mus. Bosquet; in Chalk, Norwich, Mus. J. de C. Sowerby.
M. Bosquet has admirably figured and described the several separated valves belonging to this species, and I owe to his great kindness an examination of some of them. In Mr. J. de C. Sowerby’s collection, also, there is a single specimen, attached to a Mollusc, with the four valves of the shell united together, but without the two moveable opercular valves; it cannot be positively asserted that this is the same species with that of M. Bosquet, but such probably is the case. This is the species to which I alluded in the [Introduction] to my ‘Monograph on Fossil Lepadidæ.’ It is an interesting species, from being the only known Secondary one, but in itself it is a very poorly characterised form, and I can point out no important character in the shell by which it can be recognised. The rostrum and carina, which are of nearly equal sizes, are locked together by the usual interfolding plates, and likewise to the fixed scutum and tergum; but these latter plates seem to have been less developed in M. Bosquet’s specimen than in the English. The fixed scutum has a large adductor plate, which seems to have been chipped in M. Bosquet’s specimen; this valve and the fixed tergum in all essential respects resemble the same valves in [V. Strömia]. The surface of the shell is very smooth.
The moveable scutum has its occludent margin considerably arched: the lower articular ridge is broader than the upper ridge, in which respects it resembles the same valve in [V. lævigata], but the whole valve is not so broad as in that species. There is no adductor ridge on the under surface. The moveable tergum has its upper articular ridge narrow, and slightly produced into a point on the scutal margin: in this latter respect this species also resembles [V. lævigata], but the whole valve is not so broad in proportion to its height.
3. Family LEPADIDÆ.
Cirripedia having a flexible peduncle, provided with muscles: scuta and terga, when present, not furnished with depressor muscles: other valves, when present, not united into an immoveable ring.
This Family has been fully treated of in my former volume, published by the Ray Society,[141] and I should here only have alluded to its existence, had it not been for the genus [Alcippe], which differs in so many important characters from the other members of the Lepadidæ, that formerly I did not even suspect that it could belong to this Family, and therefore deferred its examination. The genus [Alcippe] was discovered, well described and illustrated, in 1849, by Mr. Hancock; to whose very great kindness I am indebted for permission to dissect and examine his entire stock of this truly remarkable Cirripede. In the classification of the whole class I have not felt so much doubt, as whether I ought to institute a family for the reception of this genus. [Alcippe] differs from all other Cirripedes (putting on one side for the instant, the males and complemental males of Ibla and Scalpellum) in the very singular fact of being destitute of a rectum and anus;—in the three segments of the thorax, which usually support the second, third, and fourth pairs of cirri, being without any appendages;—in the fifth and sixth pairs of cirri having their inner or posterior rami metamorphosed into very singular roughened cushions or buttons, which apparently serve to triturate the food;—in the caudal appendages being muscular, and being used conjointly with the cirri;—and lastly, in the pupa having a lesser number of segments in its abdomen and caudal appendages than in (as far as I have seen) any other Cirripede. It will be thought that these characters are amply sufficient to justify the placing [Alcippe] in a separate family, more especially when the close general resemblance in the animal’s body in most of the other members of the [Balanidæ], [Verrucidæ], and Lepadidæ, is borne in mind. On the other hand, the males and complemental males of Scalpellum and Ibla must indisputably be considered as members of the Lepadidæ; yet the male of Scalpellum vulgare and ornatum has no stomach, anus, or mouth, which is a far more abnormal structure than the absence only of the anus in [Alcippe]: the cirri, also, in these same males, differ from the ordinary cirripedial type decidedly more than in [Alcippe]. Again, in the male of Ibla, all the cirri, excepting the fifth and sixth pairs, are aborted, and these two pairs are usually only uniramous; here, then, we have a decided resemblance to [Alcippe]. Hence, if we might assume that the female [Alcippe] had partially assumed characters confined to the males of the other genera, it would assuredly stand amongst the Lepadidæ. Independently of this comparison with the foregoing males, the affinities of [Alcippe] are so special to several genera amongst the Lepadidæ, that it seems unnatural to force it out of the position which it well occupies between Ibla and Anelasma, and place it in another family by itself: thus, in being bisexual, and in the general character of its very curious males, [Alcippe] shows an affinity to Ibla and Scalpellum; and to the former of these genera it is related in several particulars, such as in the body being lodged within the peduncle, and in the structure of the larval antennæ, &c.: to Anelasma and Alepas it is allied in the general character, and to a certain extent in the muscles, of the capitulum; Anelasma, also, has all its cirri to a certain degree rudimentary, and Alepas cornuta has the inner rami of the fifth and sixth pairs of cirri,—namely, the very same rami which are so curiously modified in [Alcippe],—small, destitute of muscles, and functionless for their proper purpose: to Anelasma and Lithotrya it is allied in the peculiarity of the lower end of the peduncle becoming elongated by growth, and in being imbedded; and to Lithotrya by its powers of excavation and manner of attachment. Now, I believe it generally holds good that when a form is really distinct from another group, its affinities are general, or only in a slight degree special to the members of that group. Nor, indeed, can it be asserted that [Alcippe] differs much more, somewhat more it certainly does, from the other genera, than does Anelasma, with its more singular mouth, spineless rudimentary cirri, and fimbriated peduncle; and I have never regretted having included this genus amongst the Lepadidæ. Hence, after much consideration, I have resolved to consider [Alcippe] as one of the Lepadidæ, though so curiously modified,[142] and having characters confined to the males of the other genera. Perhaps I have been in some degree influenced by the difficulty of finding external characters by which to separate [Alcippe] as a family from the other Lepadidæ.
[141] The fossil species have been described in a separate Monograph published by the Palæontographical Society. Since its publication, M. Bosquet has produced an excellent memoir, containing descriptions, with the most beautiful illustrations, of several new Cretacean species of Pollicipes and Scalpellum. The memoir is entitled a ‘Monographie des Crustacés Fossiles du Terrain Crétacé, du D. de Limbourg.’