CALLISOMA. 119 



AMPHIPODA. LYSIANASSIDES. 



NATATOR1A. 



b. Second pair of gnathopoda robust and more or less cheliform, 

 first pair feeble. 



Genus CALLISOMA, COSTA. 



Cattuoma. COSTA, Cat. del Crost. del Regno di Napoli, 1840. SPENCE 



BATE, Cat. Amph. Crust. Brit. Mus. p. 84. 



Scopelocheirus. SPENCE BATE, Brit. Assoc. Rep. 1855, p. 58. Synop. &c. 

 Ann. Nat. Hist. xix. 138, 1857. WHITE, Hist. Brit. 

 Crust, p. 168. 



Generic character. Resembles Anonyx and Lysianassa, ex- 

 cept that the first pair of gnathopoda are slender, and have the 

 dactjlos not unguiculate. Second pair robust, chelate. Pos- 

 terior pair of caudal appendages unibranched. Telson bifid. 



THE superior antenna are short and thick at the base. 

 The inferior antennae much more slender. The coxae of 

 four anterior pairs of appendages are as deep as the seg- 

 ments of the body to which they are respectively at- 

 tached. The fourth segment has the posterior margin 

 deeply excavated, to receive the anterior lobe of the 

 fifth. The first pair of arms are long and slender, and 

 have the finger terminating in a brush of hair. The 

 second pair of arms are more robust than the first, and 

 terminate in a very perfectly-formed didactyle claw. The 

 walking legs correspond with those of the other genera 

 in this subfamily ; but the caudal appendages differ in 

 having the posterior pair unibranched, and the terminal 

 plate is bifid. 



