244 GAMMARIM. 



AMPHIPODA . GAMMARIDES. 



NATATORIA 



Genus ATYLUS. 



Atylus. LEACH, Zool. Miscel. ii. pi. Ixix. MILNE EDWARDS, Hist, des 



Crust, t. iii. p. 67. SPENCE BATE, Cat. Amph. Brit. Mus. 

 p. 133. 



Iphimedia. DANA, U. S. Explor. Exped. p. 926. 



Nototropis. COSTA, Rend, della Reale Accad. delle Sci. di Napoli, p. 170, 

 1853, tav. 1, fig. 7 and 8. 



Generic character. Like Dexamine, but having the mandi- 

 bles furnished with a palpiform appendage. Peduncle of the 

 upper antennae with the third joint distinct. 



THIS genus bears a very close affinity to that of 

 Dexamine. The only important difference exists in 

 Atylus having the mandibles furnished with a three- 

 jointed appendage, which is wanting in Deocamine. We 

 have observed that in this genus there is very frequently 

 some remarkable and interesting peculiarity in the de- 

 velopment of the flagella of the antennae. In Atylus 

 carinatus of the Arctic Seas, the species on which Leach 

 founded the genus, the flagella assume a baccated or 

 bead-like character, each articulus being broader than 

 long. In A. Huxleyanus of the Antarctic regions every 

 third articulus is inferiorly dilated, and furnished with a 

 fasciculus of auditory cilia ; and in A. villosus, also 

 Antarctic, every articulus of the flagellum belonging to 

 the superior antennae is inferiorly produced at the dis- 

 tal extremity, and covered with short downy hair ; the 

 flagellum of the inferior antennae having the upper sur- 

 face similarly furnished. Thus the two antennae appear 

 to be capable of being used as grasping organs by the 

 upper and lower pairs being brought into contact with 

 each other. 



