ACANTHONOTUS. 231 



A MP HIP ODA . PH OXIDES. 



N ATA TORT A. 



Genus— ACANTHONOTUS. 



Acanthonotus. Owen, App. to Ross's Second Voyage N. W. Passage, p. xc. 



White, Hist. Brit. Crust, p. 177. Gosse, Man. 



Mar. Zool. p. 142. Milke-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. 



Genetic character. Cephalon produced antei'iorly. Antennae 

 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- 

 tennse 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 apjiendages 

 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. 



