_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.