256 GAMMA RIM. 



antennae. The body of the animal is smooth, but the 

 dorsal surface of the tail is marked by a very slight 

 carina, which terminates in a small tooth at the posterior 

 margin of the fourth segment. The eyes of the ani- 

 mal are very small in the type specimen. The superior 

 antennae scarcely reach to the half of the length of the 

 animal. The inferior antennae in the typical specimen 

 are about two-thirds the length of the superior, whereas 

 the peduncle is quite as long as, but thinner than, the 

 peduncle of the superior. The first two pairs of legs 

 are equal in size, but the hand of the second pair is 

 shorter than that of the first, and the palm a little 

 more convex. The legs are very uniform in length ; 

 the thighs of the last three being somewhat dilated. 

 The last pair of caudal appendages have the branches 

 of an equal length, but not longer than the peduncle, 

 and in the typical specimen they do not reach beyond 

 the extremity of the preceding pair. 



The figure given in the preceding page was drawn from 

 the typical specimen of Dr. Leach in the British Mu- 

 seum, and differs from that given in the " Catalogue 

 of Amphipoda of the British Museum" in a few de- 

 tails, the most important of which are the length of 

 the last pair of caudal appendages, and the length of 

 the inferior antennae. The latter distinction is not im- 

 portant, since it depends upon the length of the flagel- 

 lum only, which is very liable to vary, whereas the 

 peduncle is quite as long and important as the peduncle 

 of the superior. The former difference may perhaps be 

 of greater importance, but it requires much considera- 

 tion before we can separate into distinct species animals 

 upon so slight a variation, particularly as we have ob- 

 served specimens in which the length of these branches 

 were intermediate between the types of Leach and Ed- 



