AGANTHONOTUS. 
AMPHIPOBA. 
NAT ATOM A. 
231 
PHOXIBES. 
Genus— AGANTHONOTUS. 
Acanthonotus. Owen, App. to Ross’s Second Voyage N. W. Passage, p. xc. 
White, Hist. Brit. Crust, p. 177. Q-osse, Man. 
Mar. Zool. p. 142. Milne-Edwards, Hist. Crust, 
t. iii. p. 24. Spence Bate, Cat. Crust. Amph. 
Brit. Mus. p. 126. 
Vertumnus, Leach MSS. White, Cat. of Crust. Brit. Mus. 1847. 
Generic character. Cephalon produced anteriorly. Antennas 
simple, subequal. Mandibles with a tri-articulate appendage. 
Coxae narrow, deep, and pointed, except the two last, those of 
the fourth legs lunate, with a strong tooth. Gnathopoda slender, 
feeble, subchelate. Pereiopoda subequal. Dactyla unguiculate. 
Posterior pair of pleopoda biramous. Telson single, cleft at the 
apex. 
The front of the head is considerably produced into 
a point, curved downwards. The segments of the body 
are short, whilst those of the tail are long. The an- 
tennae are nearly of the same length (about one-fourth of 
the length of the animal) ; the superior do not possess a 
secondary appendage. The arms are uniform, subequal, 
slender, feeble, and subchelate. The coxae of the first 
four pairs of legs are deep, narrow, and pointed, those 
of the fourth pair are sickle-shaped, having, moreover, a 
strong central tooth on the posterior margin. The 
walking legs are subequal, and have the fingers terminat- 
ing in a sharp nail. The last pair of caudal appendages 
consist of two styliform branches, and the terminal plate 
is single, but cleft at the apex. 
This genus was founded by Professor Owen, for a 
species of Amphipod brought from the Arctic Regions by 
Sir John Clark Ross. 
