94 



have quite escaped the attention of earlier authors. I have found it perfectly 

 constant in all the specimens more closely examined by me. 



Occurrence. This species is of very common occurrence around Christi- 

 ania, being found, often in great abundance, in shallow ditches and pools with 

 grassy bottom. In habits it ressembles the preceding species, though being 

 perhaps somewhat less agile. 



Distribution. Throughout Europa, Central Asia, North, America. 



29. Cyclocypris serena (Koch). 



(PI. XLIII, fig. 3). 

 Cypris serena, Koch, Deutsch lands Crustaceen, H. XXI. 22. 



Syn: Cvpris Icevis, Brady (not O. Fr. Miiller). 

 , Cpclocypris ovum serena, Aim. 



Specific Characters. Female. Shell seen laterally, broadly oval in shape, 

 greatest height in the middle and almost attaining 3 /4 of the length, dorsal 

 margin boldly and rather evenly arched throughout, ventral margin not at all 

 sinuated, both extremities blundtly rounded and nearly equal; seen dorsally, 

 broadly ovate in outline, greatest width somewhat behind the middle and equal 

 to the height, anterior extremity somewhat more narrowed than the posterior. 

 Surface of valves smooth and polished, being clothed at each extremity with 

 delicate hairs. Posterior legs with the terminal joint scarcely half as long as 

 the penultimate one, middle apical seta about the length of the terminal joint 

 and simply curved at the end. Caudal rami of moderate size and slightly 

 curved, dorsal edge nearly smooth, with only very slight trace of an armature 

 at the base, apical claws comparatively more slender than in the preceding 

 species, the distal one fully attaining half the length of the ramus. 



Male closely resembling the female both in size and in the shape of the 

 shell. Prehensile palps of maxillipeds less conspicuously unequal than in C. 

 globosa, the dactylus of the right one being comparatively smaller, though much 

 broader than on the left palp. Copulative appendages and ejaculatory tubes 

 likewise differing in shape conspiciously from those parts in the said species. 



Colour in both sexes dark olivaceous brown. 



Length of adult female amounting to 0.60 mm. 



Remarks. I am by no means convinced that the above-described form 

 is in reality identical with Cypris serena of Koch, which I should be more 

 inclined to refer to the preceding species. As I however feel some reluctance 

 in augmenting the long list of specific names proposed within the present 



