236 
GAMMA RIM!. 
AMP HIP OR A. 
NATATORIA. 
OA MM A RIDES. 
Genus— DEXAMINE. 
Dexamine. Leach, Edin. Encyc. vii. p. 483. Spence Bate, Cat. 
Amph. Brit. Mus. p. 130. 
Acanthonotus (pars). Milne -Edwards, Ilist. des Crust, iii. p. 25. 
Generic character. Superior antennae having the third joint 
of the peduncle reduced in size, so as to resemble the first 
articulus of the flagellum ; without a secondary appendage. 
Mandibles having no appendage. Gnathopoda feeble, subche- 
late. Telson single, divided. 
In this genus the antennae are of moderate length, slen- 
der, and nearly of corresponding proportions ; both pairs 
are remarkable for the absence of a joint in the pe- 
duncle ; but this absence is probably more apparent than 
real, arising from the last joint in each being reduced to 
the form and appearance of the articuli of the flagellum. 
The mandibles are not furnished with an appendage, a 
peculiarity especially characteristic of the Orchestid^e. 
The first two pairs of legs are subchelate, although 
slender. The coxae of the four anterior pairs of legs 
are subequally deep and rounded ; those of the three 
posterior are scarcely more than half as deep as the 
preceding. The posterior pair of caudal appendages 
are two-branched, and the central terminal plate is 
single, but constantly divided to a considerable extent 
down the middle. 
This genus was founded by Dr. Leach, to receive a 
species described by Montagu under the name of Cancer 
( Gammarus ) spinosus , but it was not accepted by Prof. 
Milne-Ed wards, who referred Montagu’s species to the 
genus Acanthonotus. 
