^48 



GAMMARID^. 



AMPHIPODA. 



NATATORU. 



GAMMARIDES. 



^ ATYLUS GIBBOSUS. 



Specific character. Fourth segment of the pleou dorsally produced into 

 ii blunt hump-like tooth. Pereiopoda, having tlie mera long and the carpi 

 short and dilated at the extremity, spinose. 



Length ^^ inch. 



AtyJus fjihhosus. 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, I'esembled 

 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 



