Phyllopod Crustacea of Japan. 



By 



C. Ishikawa. 



(PI. XX.) 



DAPHNIA MOKSEL* 



Parthenogenetic female (Fig. 1). 



Tha length of the largest specimens examined measured over 4 mm., 

 the spine of the carapace measuring 1,3 mm.; it thus attains nearly the 

 size of the Europian Daphnia magna. 



The general shape of the body is oblong oval, the greatest breadth 

 being nearly equal to the height. 



The dorsal ridge of the head is slightly slanting forward, and is 

 defined from the carapace by a shallow but distinct impression posteriorly. 

 Anteriorly it forms an even curve with its ventral margin, which is 

 slightly concave behind the eye, and runs out to form an acute-angled 

 "rostrum," The posterior margin of the rostrum runs in a wavy line 

 towards the base of the antennae. The forinx is rather prominent. 

 It begins from the dorsal ridge of the head above the eye, and runs 

 backwards in a slight curve to the base of the antennse where it forms a 

 sudden bent, and runs out again backwards and slightly downwards and 

 making an obtuse angle behind the antennae, continues to end at the 

 origin of the free border of the carapace. The dorsal aspect the head 

 (Fig. 2) is, owing to the great development of the fornices, nearly as 

 broad as the body, with the dorsal ridge standing out in the median line 

 as an angular projection. 



The carapace, viewed from the side, exhibits an oval form with the 



* Dedicated to my first teacher in Zoology, Prof. Ed. S. Morse, Salem. Mass., U. S. A. 



