252 GAMMARID.E. 



AMPlllPODA . UAMMAR[DEtS. 



NATATORIA. 



Genus— PHERUSA. 



Phcrusa. Leach, Edin. Encyc. vii. p. 432. Trans. Liun. Soc. xi. p, 360. 



Enc. Brit. Suppl. p. 426.- Des.marest, Cousid. sur. Crust. 



p. 269, p]. xliv. Spenck Bate, Cat. Aniph. Brit. Mu?. 



p. 143. (Not of Koch, DeiitscLlamla Criistticeeu, &c. Heft. 



xxix. pi. 24, which is an Isopod. ) 

 Amphitoe. Milne Edwards, Ann. des Sci. Nat. t. xx. p. 376. Hist, dcs 



Crust, iii. p. 32. 

 AmpMtlwc. Dana, United States' Exijlor. Exped. p. 910 (part). 



Generic character. Like Atrjlus, but telson not divided. 

 Gnatliopoda small. 



This genus is very near to Atylus ; in fact, the de- 

 marcation through some of the exotic species is so 

 feeble, that some carcinologists may doubt the pro- 

 priety of our separating them. Atylus Huxleyanus, from 

 Hermit Island (Antarctic Ocean) indeed might be al- 

 lotted to either genus, since the cleft in the terminal 

 caudal plate is reduced to a mere indentation of the 

 apex. But since, in this and other nearly-allied genera, 

 there are many species which can be grouped into sepa- 

 rate divisions, we think that it will be found convenient 

 to consider them as forming separate genera. 



In addition to the entire central caudal plate, which 

 is the chief distinction between this genus and Atylus, 

 the difference in the form and size of the gnatliopoda 

 separates it from Calliope. 



