CALLISOMA. 
119 
AMPHIPODA. LYSIANASSIDES. 
NATATORIA. 
b. Second pair of gnathopoda robust and more or less cheliform, 
first pair feeble. 
Genus — CALLISOMA, Costa. 
Callisoma. Costa, Cat. dei 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 
dactylos not unguiculate. Second pair robust, chelate. Pos- 
terior pair of caudal appendages unibranched. Telson bifid. 
The superior antennae 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. 
