1890.] : l _ G. M. Giles — Descriptions of new Indian Amphipods. 73 



Its nearest allies appear to be 0. orientate, Dana, and 0. cristatum, 

 Thomson, from the former of which it differs in its superior antenna 

 being proportionally smaller, in the comparative shortness of the dacty- 

 lopodite of the second gnathopod, and in the details of the armature of 

 the hinder pleopoda ; and from the latter in both pairs of antennas being 

 proportionally smaller and in wanting any marked crest on the hinder 

 part of the thorax. 



The head is subquadrate, rather deeper than long, its length form- 

 ing only one-eighth of the entire body length. 



The small etje is placed on a prominence opposite the origin of 

 the antenna. 



The thorax is long, forming three-sevenths of the entire length. Its 

 segments are long and slender, the anterior and posterior ones being- 

 larger than those at its mid length, and the fifth segment exceptionally 

 small. 



The abdomen is small and, like the thorax, slender. Its first 

 three segments are rather shorter than average thoracic segments. The 

 fourth, though narrow, is longer than the others, while the fifth and 

 sixth are extremely small. 



The telson is small and laminar, and is armed with a few short, 

 stiff hairs. 



The antennule is fully as long as the head and first four thoracic 

 segments. More than three-fourths of its length are formed by the ped- 

 uncle ; the first joint of which, though very stout, is shorter than either 

 of its two other joints, while the second is considerably the longest. 

 There is a minute secondary appendage, consisting of four short 

 joints. The flagelluin is only as long as the first joint of the peduncle ; 

 it too consists of four joints, the first of which forms quite half its 

 length. The entire inferior sui'face of the appendage is armed with 

 closely placed long hairs. 



The antenna is as long as the head, thorax, and first two abdominal 

 segments ; it is very stoutly built and adapted for climbing. The first 

 three joints of its peduncle are short and together as long as the 

 fiagellum, while the two distal joints are subequal, and form two-thirds 

 of the entire length of the organ. The fiagellum consists of two stout 

 long joints, which are armed with strong hooked spines. The entire 

 lower surface of the peduncle being furnished with long stiff hairs, like 

 those on the superior antenna. Its last joint is armed with two paira 

 of stout, hooked spines, and by a hooked terminal nail. 



The gnathites could not be closely examined, but it could be 

 seen that the mandibular appendage is large and clawed, and that the 

 maxilliped is exceptionally large and pediform. 

 10 



