SCALPELLUM. 13 
I may further state, that in the several Orders of Cirripedia such important differences 
of structure are presented, that there is scarcely more than one great character by which all 
Cirripedia may be distinguished from other Crustacea: this character is, that they are 
attached to some foreign object by a tissue or secretion (for at present I hardly know which 
to call it), which debouches, in the first instance, through the prehensile antennz of the 
larva, the antennze being thus embedded and preserved in the centre of the basis. The 
cementing substance is brought to its point of debouchement by aduct, leading from a 
gland, which (and this is perhaps the most remarkable point in the natural history of the 
Class) is part of and continuous with the branching ovaria. When we look at a Cirripede, we, 
in fact, see only a Crustacean, with the first three segments of its head much developed and 
enclosing the rest of the body, and with the anterior end of this metamorphosed head fixed 
by amost peculiar substance, homologically connected with the generative system, to a rock 
or other surface of attachment. 
Genus—SCALPELLUM. 
ScaLpeLLuM. Leach. Journ. de Physique, t. Ixxxv, July, 1817. 
Lepas. Linn. Systema Nature, 1767. 
Poutticipes. Lamarck, Animaux sans Vertebres. 
Potyitepas. De Blainville. Dict. des Sc. Nat., 1824. 
SMILium (pars generis). Leach. Zoolog. Journal, Vol. 2, July, 1825. 
CaLantica (pars generis). J. EH. Gray. Annals of Philosophy, vol. x, (2d series,) 
Aug. 1825. 
THALIELLA (pars generis). J. H. Gray. Proc. Zoolog. Soc., 1848. 
ANATIFA. Quoy et Gaimard, Voyage de l’ Astrolabe, 1826—34. 
XIPHIDIUM (pars generis). Dixon. Geology of Suffolk, 1850. 
Valvis 12 ad 15: Lateribus verticells inferioris quatuor val sex, lineis incrementi 
plerumque convergentibus ; Subrostrum rarissime adest: Pedunculo squamifero, rarissime 
nudo. 
suspect to be auditory organs; this part, therefore, I think, must unquestionably consist of the first two or 
three segments of the head: within it, even before the larva moults, the incipient strizeless muscles and 
ovaria of the peduncle can be distinctly traced: immediately after the moult, we see this anterior part 
converted into a perfect peduncle; and for some time afterwards certain coloured marks, indicating the 
former position of the (so called) olfactory cavities and of the cast-off compound eyes, are still preserved. 
The prehensile antennz are not cast off, for they are fastened down by the cementing substance, and are 
thus preserved in a functionless condition, with their muscles absorbed; after a time even the corium is 
withdrawn from within them. From the above and other coloured marks, and from the antennze being 
preserved, it is easy to point out, in the peduncle of a young though perfect Lepas, the exact point which 
each part occupied in the head of the natatory larva. 
Since the above was written, I find that Loven has taken the same view of the homologies of the 
external parts of the Cirripedia; in his description of his Alepas squalicola, (Ofversigt of Kongl. Vetens., &c., 
Stockholm, 1844, pp. 192—4,) he uses the following words: “‘Capitis reliquae partes, ut in Lepadibus semper, 
in pedunculum mutate et involucrum,” &c.; his involucrum is the same as the Capitulum of this work. 
