ON A NEW 1CHTHYOXENUS FROM LAKE ÜIWA. 



1 3 I' 



longer than the exopodite (fig. 10, b). Posterior margin of both' rami of 

 first and second pairs, and also of the exopodite of the third, fourth and 

 fifth pairs are minutely serrated, while the endopodite of the last three 

 pairs show no such serration. Inner edge of the protopodite of each 

 plcopod is also more or less serrated. No hairs present on all pleopods. 

 Uropod is a little longer than the terminal metasome segment ; its exopo- 

 dite somewhat longer than endopodite ; the former more or less lanceolate, 

 and the latter elongate-oval in outline ; hairs absent on both. Terminal! 

 segment of metasome of a somewhat triangular shape, its posterior end 

 narrow and rounded ; the posterior margin minutely serrated ; without, 

 hairs in any part. 

 Measurements of typical larva : 



Length of dody, 2.8S mm. 



Length of cephalon, 0.46 ,, 



Length of metasome, 1.24 ,, 



Length of terminal metasome segment, 0.49 ,, 



Breadth of body (mesosome), 0.S9 ,, 



Breadth of metasome, °-53 >, 



Tokyo, Jan. 25, 19 16. 



