9 2 



CRUSTACEA CIRRIPEDIA 



CHAP. 



in the skin of whales, the shell of the first-named being of a 

 highly complicated structure with hollow triangular compartments 

 into which the mantle is drawn out. 



Xenobalanus ijlolicipitis lives attached to various Cetacea. 

 and is remarkable for the rudimentary condition of its skeleton, 

 the six plates of which form a mere disc of attachment from 

 which the greatly elongated naked body rises, resembling one of 

 the naked Stalked Barnacles. 



Fam. 4. Tetrameridae. In this family only four skeletal 

 plates are present (Fig. 63, C). This family is chiefly confined 

 to tropical seas or those of the Southern hemisphere. The chief 

 genera are Tetraclita and Pyrgoma, found in British seas. 



Sub-Order . 3. Acrothoracica. 



(h-uvel includes in this sub-order four genera (Alcippe, 

 Koclilorine, and Lifhoglyptes), the species of 



--Or 



M MO 



O' 



A B 



FIG. 64. Alcippe lampas. A, ? , x about 10, seen from the right side, with part of the 

 rijrht half oi'thf animal removi-d ; B, dwarf male, x about 30. A.M, adductor imi.M'lr ; 

 An, antenna ; I', 1st pair of cirri ; Or, posterior thoracic appendages ; E, eye ; 6', 

 testis ; M.c, mantle-cavity; 0, ovary; P, penis; T, penultimate thoracic seg- 

 ment ; 1'. vesicula seminalis. (After Darwin.) 



which live in cavities excavated in the shells of molluscs or in 

 the hard parts of corals. 



Darwin discovered and described CryptopJiialus minutus, and 

 placed it in a sub -order Abdominalia, believing that it was 



