The animal’s body is included within the capitulum, within what I call the sack (see [Pl. IV], [figs. 2] and [8´ a], and [Pl. IX], [fig. 4]). The body consists of the thorax supporting the cirri, and of an especial enlargement, or downward prolongation of the thorax, which includes the stomach, and which I have called the prosoma. ([Pl. IX], [fig. 4 n]). The cirri are composed of two arms or rami, supported on a common segment or support, which I call the pedicel. The caudal appendages are two little projections, either uni-or multi-articulate ([Pl. IV], [fig. 8´ a]), on each side of the anus, and just above the long proboscis-like penis. On the thorax and prosoma, or on the pedicels of the cirri, there are in several genera, long, thin, tapering filaments, which have generally been supposed to serve as branchiæ; these I call simply filaments, or filamentary appendages ([Pl. IX], [fig. 4 g-l]). The mouth ([fig. 4 b]) is prominent, and consists of palpi soldered to the labrum; mandibles, maxillæ, and outer maxillæ, these latter serve as an under lip; to these several organs I sometimes apply the title used by Entomologists, of “trophi.” Beneath the outer maxillæ, there are either two simple orifices or tubular projections; these, I believe, serve as organs of smell, and have hence called them the olfactory orifices. Within the sack, there are often two sheets of ova ([Pl. IV], [fig. 2 b]), these I call (after Steenstrup, and other authors) the ovigerous Lamellæ; they are united to two little folds of skin ([Pl. IV], [fig. 2 f]), which I call the ovigerous Fræna.

From the peculiar curved position which the animal’s body occupies within the capitulum, I have found it far more convenient (not to mention the confusion of nomenclature already existing) to apply the term Rostral instead of ventral, and Carinal instead of dorsal, to almost all the external and internal parts of the animal. Cirripedes have generally been figured with their surfaces of attachment downwards, hence I speak of the lower or Basal margins and angles, and of those pointing in an opposite direction as the Upper; strictly speaking, as we shall presently see, the exact centre of the usually broad and flat surface of attachment is the anterior end of the animal, and the upper tips of the Terga, the posterior end of that part of the animal which is externally visible; but in some cases, for instance in Coronula, where the base is deeply concave, and where the width of the shell far exceeds the depth, it seemed almost ridiculous to call this, the anterior extremity; as likewise does it in Balanus to call the united tips of the Terga, lying deeply within the shell, the most posterior point of the animal, as seen externally.

I have followed the example of Botanists, and added the interjection [!] to synonyms, when I have seen an authentic specimen bearing the name in question.

Every locality, under each species, is given from specimens ticketed in a manner and under circumstances appearing to me worthy of full confidence,—the specific determination being in each case made by myself.

Class—CRUSTACEA. Sub-Class—CIRRIPEDIA.

Family—LEPADIDÆ.

Cirripedia pedunculo flexili, musculis instructo: scutis[3] musculo adductore solummodô instructis: valvis cæteris, siquæ adsunt, in annulum immobilem haud conjunctis.

Cirripedia having a peduncle, flexible, and provided with muscles. Scuta[3] furnished only with an adductor muscle: other valves, when present, not united into an immovable ring.

[3] The meaning of this and all other terms is given in the Introduction, at [pp. 3-7.]