[ Figure I.
CAPITULUM. ]

Figure II.
SCUTUM of LEPAS.

Figure III.
TERGUM of LEPAS.

Although the present volume is strictly systematic, I will, under the general description of the Lepadidæ, give a very brief abstract of some of the most interesting points in their internal anatomy, and in the metamorphoses of the whole class, which I hope hereafter to treat, with the necessary illustrations, in detail. I enter on the subject of the metamorphoses the more readily, as by this means alone can the homologies of the different parts be clearly understood.

On the Names given to the different parts of Cirripedes.

I have unwillingly found it indispensable to give names to several valves, and to some few of the softer parts of Cirripedes. The accompanying figure of an imaginary Scalpellum includes every valve; the two most important valves of Lepas are also given, in which the direction of the lines of growth and general shape differ from those of Scalpellum as much as they do in any genus. The names which I have imposed will, I hope, be thus acquired without much difficulty.

Whoever will refer to the published descriptions of recent and fossil Cirripedia, will find the utmost confusion in the existing nomenclature: thus, the valve named in the woodcut the Scutum, has been designated by various well-known naturalists as the “ventral,” the “anterior,” the “inferior,” the “ante-lateral,” and the “latero-inferior” valve; the first two of these titles have, moreover, been applied to the rostrum or rostral valve of sessile Cirripedes. The Tergum has been called the “dorsal,” the “posterior,” the “superior,” the “central,” the “terminal,” the “postero-lateral,” and the “latero-superior” valve. The Carina has received the first two of these identical epithets, viz. the “dorsal” and the “posterior;” and likewise has been called the “keel-valve.” The confusion, however, becomes far worse, when any individual valve is described, for the very same margin which is anterior or inferior in the eyes of one author, is the posterior or superior in those of another; it has often happened to me that I have been quite unable even to conjecture to which margin or part of a valve an author was referring. Moreover, the length of these double titles is inconvenient. Hence, as I have to describe all the recent and fossil species, I trust I may be thought justified in giving short names to each of the more important valves, these being common to the pedunculated and sessile Cirripedes.