PROTEOLEPAS B1VINCTA. 589 



Proteolepas bivincta. PI. 24, 25, figs. 1 — 7. 



Hab. — Parasitic within the sack of the Alepas cornuta, from St. Vincent's, 

 West Indies, Brit. Mus. 



General Appearance* — The entire animal, as already 

 remarked, curiously resembles, at the first glance, the larva 

 of some insect. It is rounded, but somewhat compressed, 

 and tapers gently towards the posterior end. It lies curved 

 in an arc, the ventral surface being concave, and the dorsal 

 convex, but a little flattened dorsally at the anterior and 

 blunter end. Its length, if straightened, would rather 

 exceed one fifth of an inch. The body consists of eleven 

 segments, which, excepting the three terminal, are conspi- 

 cuously plain. The first segment is surmounted by a 

 rather small mouth, which any one would, assuredly, at first 

 consider as the entire head, though he would in vain search 

 here for eyes, antennae, or other parts of the three anterior 

 cephalic segments. On the dorsal surface, low down on 

 the second segment of the body, two, quite flexible, thin, 

 but strong, flattened threads arise, which terminate in a pair 

 of prehensile antennae, having the usual cirripedial struc- 

 ture. Prom the penultimate or disc segment of these 

 antennae, cement has been excreted, by which the antennae 

 are firmly cemented low clown to the rostral end of the 

 sack of the cirripede, the Alepas cornuta, on which it 

 is parasitic : hence Proteolepas lies with its back down- 

 wards, and with its ventral concave surface fitting the convex 

 body of the Alepas : its mouth lies under the middle of 

 the soft prosoma of the latter^ cirripede, which I cannot 

 doubt that it lacerates and sucks. 



Mouth. — The mouth is suctorial, and is constructed on a 

 different plan from that in any other cirripede, or, indeed, in any 



* I may be permitted to premise, that though I procured only a single 

 specimen, yet perceiving its very singular nature, I took such care and length 

 of time in the dissection, and repeated every observation so many times that 

 I think reliance may be placed on the description here given. Fortunately I 

 had acquired, from dissecting many much smaller specimens of various cirri- 

 pedes, all the advantage which full experience could give me, when I commenced 

 on Proteolepas. 



