148 C. ISHIKAWA. 



The lateral view of the carapace presents a ])L-oad oval shape with 

 the dorsal and ventral sides of nearly the same cai'veture as in Morsei, 

 the dorsal carve also changing much with the contents of the breedin;^ 

 chamber as in that species. It also appears to be more curved in large 

 animals than in small ones in which the dorsal hne runs nearly straight 

 to the base of the spine. The position of the spine changes also much 

 according to the size of the animal, being placed higher np in small 

 animals than in large ones (compare Fig. 1 & 5). This spine is shorter 

 than in D. IMorsei, but is longer than in D. pulex. Perhaps it is of the same 

 length as that of D. pennata of which Hellich says that it is much longer 

 than in D. pulex.* In some few specimens it is either entirely wanting 

 or is represented by a very short knob-like protuberance. It is armed 

 with four rows of spinules as usual, Ihe dorsal rows continuing only for 

 a short way along the dorsal ridge of the carapace. The posterior half 

 of the inferior border of the carapace is also beset with spiimles. 



The sculpture of the shell is as usual rhombic, hexagonal oi" pen- 

 tagonal, and its matrix of the same usual structure, the star-shaped figures 

 being formed at the ends of the pillars of connective tissue fibres, thus 

 giving to the shell the same appearance as that of D. Morsei, i.e. the net- 

 like lines with the star-shaped figures. There is, however, much 

 variation as to the relative development of the two. In some cases the 

 sculpture of the shell is indistinct while the star-shaped figures are much 

 developed, so that the shell appears by cursory observation only as 

 punctuated, while in others the reverse is the case. 



The shell-gland (Fig. 1 a.) is of usual shape. 



The dorsal view of the carapace (Fig. 2) is much narrower than in 

 D. Morsei, and roughly presents a rectangular form, the two long sides 

 of it, which is formed by the lateral border of the carapace, being but 

 slightly curved. 



The eye is large, as in preceding species, situated close to the 

 anterior border of the head ; its crystalline lenses are large and are of a 



* Bohuslav Hellicli: Die Cladoceren Bolimens (Arcliiv dei- Natiu'w. lyandesdurolifor- 

 schnng von Bohmen, ILI Bd. IV Abtheikmg, II Heft). 1877, 



