2U 
GAMMARIDiE. 
AMPHIPODA. GA MMA RIDES. 
NAT ATOM A 
Genus— ATYLUS. 
Atylus. Leach, Zool. Miscel. ii. pi. lxix. 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 Dexamine . 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, nnd 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. 
