ON A NEW EPICARIDAN ISOPOD. 



529 



appearance as that of the adult, except in being generally somewhat 

 more slender. The fourth joint is ovoid in shape ; the fifth is claw- 

 like and comparatively very thin and long. Legs of the posteriormost 

 one or two pairs are usually slightly smaller in size than more ante- 

 riorly situated ones. Measurements taken from the first left leg of a 

 larva are as follows : 



Length of ist or proximal joint, 0,040 mm. 



Length of 2nd joint, 0,026 mm. 



Length of 3rd joint, 0,012 mm. 



Length of 4th joint, 0,034 mm - 



Length of exposed claw, 0,024 mm. 



The metasome is somewhat smaller than the mesosome. Its 

 posterior end is broadly rounded, excepting the presence of a short 

 median process. It consists of six segments, but is not so distinctly 

 segmented as in the mesosome. There exist five pairs of well de- 

 veloped pleopods, each of which bifurcates into a ventral and a dorsal 

 ramus, the former usually having a single long bristle and the latter 

 two or more of same. The dorsal ramus is articulated to the basal 

 joint, while the ventral one represents only an off-shoot of the latter. 

 The bristles of pleopods are about 76// long. The uropod is large and 

 powerful, with two equally long branches, each measuring 0,104 mm. 

 in length. 



Tokyo, Oct. 25, 191 3. 



