

ceeding half the length, dorsal margin gibbously arched in the middle and 

 sloping rather steeply both in front and behind, ventral margin very slightly 

 sinuated, anterior extremity obliquely rounded, posterior somewhat broader and 

 likewise obliquely rounded off; seen dorsally, very broady ovate in outline, 

 with the greatest width in the middle and somewhat exceeding the height, 

 both extremities pointed, the anterior more so than the posterior. Surface of 

 shell smooth and clothed with fine hairs. Natatory setae on posterior antennae 

 very much reduced, not nearly extending to the middle of the succeeding joint. 

 Spines on outermost masticatory lobe of the maxillae quite smooth. Caudal 

 rami rather narrow and nearly straight, with the dorsal edge smooth, distal 

 claw about half the length of the ramus, dorsal bristle slightly longer than the 

 apical one. 



Colour pale whitish yellow, slightly clouded dorsally behind the ocular 

 region. 



Length of adult female about 1 mm. 



Male unknown. 



Remarks. The identity of the above-described form with Cypris pigra 

 of Fischer seems to be quite ascertained, and the specific name tumefacta, 

 under which this form has generally been recorded, must of course cede the 

 older name proposed by Fischer. It is a very distinct and easily recognisable 

 species, differing considerably in its general appearance from the other forms 

 included in the present genus, though its place within it may be regarded as 

 unquestionable. 



Occurrence. I have taken this form very abundantly in a shallows ditch 

 near Christiania, and have also met with it in our largest lake, Mj0sen at 

 Hamar, where it occurred not rarely on a woody bottom at a depth of 2 4 

 fathoms. The animals are found slowly crawling on the bottom, being quite 

 unable to move freely in the water. 



Distribution. Sweden, British Isles, Germany, Switzerland, Russia. 



54. Prionocypris olivacea (Brady & Norman). 



(PI. LXll). 



Herpetocypris olivacea, Brady & Norman, Monograph of Mar. and Freeh water Ostracoda 1889, 



p. 89, PI. 1, figs. 3, 4. 

 Syn: Ilyodromus oiivaceus, Brady & Norman 1896. 



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

 greatest height a little in front of the middle and about equalling half the 

 length, dorsal margin gently arched, ventral slightly sinuated, anterior extremity 



