248 
GAMMARIDiE. 
A MPHIP OB A . GA MM A BIDES. 
NATAT0R1A. 
Specific character. Fourth segment of the pleon dorsally produced into 
a blunt hump-like tooth. Pereiopoda, having the mera long and the carpi 
short and dilated at the extremity, spinose. 
Length 5 4 0 inch. 
Atylus gibbosus. Spence Bate, Cat. Amph. Crust. Brit. Mus. p. 137, pi. 
xxvi. fig. 3. 
The fourth segment of the tail is elevated into an 
obtusely-pointed tooth, which, in the specimen originally 
described, in its contracted or rolled position, resembled 
a hump. In other specimens, particularly when the ani- 
mal is extended, it assumes more the character of a sharp 
tooth. The eyes are nearly round. The antennae are nearly 
of the same length, and quite half that of the animal ; 
the second joint of the superior antennae is a little longer 
than the first; the peduncle of the inferior antennae 
reaches beyond that of the superior. The first two 
pairs of legs are feeble, the hands are small, the se- 
cond being rather the larger. The five succeeding pairs 
of legs (the true walking feet) exhibit a striking fea- 
ture : the metacarpal joints are long, and gradually 
increase in diameter towards the distal extremity ; all 
the carpal joints or wrists are exceedingly short, and 
