REPORT ON THE ISOPODA. 27 



increase in length, the last being the largest and about equal to the anterior segments ; 

 these segments are of course curved backwards ; their lateral margins are rounded, and 

 the rounded epimera are far more conspicuous than in the anterior segments of the 

 thorax. 



The abdominal shield is preceded by a single free segment, as in other species of this 

 and allied genera. 



The abdominal shield itself is oval, ending in an obtusely rounded extremity ; near to 

 this on either side are articulated the uropoda. 



The antennules are very much like those of the last species but differ in that the 

 flagellum is only three jointed. 



The antennae are unfortunately broken off at the fourth joint. They do not appear 

 to differ from those of other species, so far as regards the basal joints of the peduncle. 



Of the thoracic appendages only the third and seventh have been preserved ; it is 

 clear, however, from these, that the present species agrees with other species of its genus, 

 in that the posterior are longer than the anterior thoracic appendages. The posterior 

 pair of thoracic appendages are about as long as the body itself. 



These appendages are distinguished, Hke those of other species of the genus, by the 

 great length and slenderness of the fifth joint, which like the preceding is moderately 

 spiny. The terminal joint is short and has two subequal claws. 



The uropoda are very much like those of the last species, being short conical 

 appendages with a few hairs at the apex. 



Kerguelen ; depth, 30 fathoms. 



Pleurogonium, G. 0. Sars. 

 Pleurogonium (Pleuracantha), G. 0. Sars, Forhandl. Vidensk. Selsk., 1863, p. 219. 



Three small Isopoda from Tristan da Cuuha and Kerguelen appear to belong to this 

 genus, which may be defined as follows : — 



The anterior region of the body (head and thorax) greatly dilated and depressed, the 

 three posterior segments of the thorax much narrower than the anterior and directed 

 backwards. Head small, obtusely pointed or rounded anteriorly ; eyes absent. 

 Abdominal segments fused into an oral pointed abdominal shield, with the exception of 

 the first segment, which remains distinct. Antennae moderately long, the anterior pair 

 equal to, or shorter than the posterior pair ; flagellum of antennules short, two or three 

 jointed. First pair of thoracic appendages stout and cheliform ; following appendages 

 simdar in structure, but increasing progressively in length ; furnished with a single 

 terminal claw. Abdominal operculum of female large, with a sharply pointed apex. 

 Uropoda extremely short, projecting but slightly beyond the margin of the caudal shield, 

 biramose, each ramus composed of a single point, the inner larger than the outer. 



