92 



CRUSTACEA CIRRIPEDIA 



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

 highly complicated structure with hollow triangular compartments 

 into whicli the mantle is drawn out. 



Xcnohalanus glohicipiiis lives attached to various Cetacea, 

 and is remarkable for the rudimentary condition of its skeleton, 

 tlie six plates of which form a mere disc of attacliment from 

 wliich 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 Soutliern hemisphere. The chief 

 genera are Tetraclita and Pyrgoma, found in British seas. 



Sub-Order 3. Acrothoracica. 



Gruvel includes in this sub-order four genera (Alcippe, 

 Cryptophialus, Kochlorine, and Lithoglyptes), the species of 



AM 



A B 



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

 right half of the animal removed ; B, dwarf male, x about 30. A . M, adductor muscle ; 

 All, antenna; C, 1st pair of cirri ; Or, posterior thoracic appendages ; E, eye ; G, 

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

 ment ; r. vesicula semiualis. (After Darwin.) 



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

 the hard parts of corals. 



Darwin discovered and described CryiJtophialus mmutus, and 

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



