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by most recent authors, though Dr. Aim has uttered some doubt thereon. The 

 said author refers this species to the genus Potamocypris, Brady (= Para- 

 cypridopsis, Kaufmann); but this can scarcely be sanctioned, because that ge- 

 nus is characterised by the quite rudimentary condition of the natatory setae 

 on the posterior antennae and the consequent want of swimming power. The 

 very conspicuous asymmetry of the valves renders the present Ostracod easily 

 recognisable from most of our other Cypridae; but this asymmetry is only 

 apparent in fully grown specimens. In the immature state of the animal the 

 valves are nearly equal (see the fig. given on the plate of such a specimen). 



Occurrence. I have taken this form in several places of our country, and 

 as far north as Sels0vik, lying just within the polar circle. It is found in 

 shallow grassy ponds and swamps, and, though more generally keeping at 

 the bottom, the animals are seen at times swimming rather quickly about in 

 the water. All the specimens examined by me were of the female sex, and 

 I do not have any notice of the male of this form having ever been observed. 



Distribution. Throughout Europe, Central Asia, (?) South America. 



Subfam. 5. Darwinulinae. 



Remarks. This subfamily only comprises a single genus, Darwinula, 

 which by most authors has been recorded as the type of a distinct family of 

 the suborder Podocopa. Yet referring the reader to the considerations set forth 

 in the earlier parts of the present Volume and to my proposal of only admit- 

 ling 2 real families of the Podocopa, I have found it more appropriate to 

 record this genus as the type of only a subfamily, which I have felt justified 

 to class within the family Cypridae, as here defined. True, the Cyprid characters 

 would seem so be somewhat less clearly manifested in this subfamily than in 

 most of the preceding ones; but jet I think that there is full evidence of its 

 nearer approach to the Cyprid than to the Cytherid type. The characters of 

 the genus given below will, I think, show this more clearly. 



Gen. 29. Darwinula. Brady & Norm. 1889. 



Syn : Polycheles, Brady. 

 Darwinella, Brady. 



Generic Characters. Shell more or less cuneate in shape, narrowed in 

 front, expanded behind. Valves thin and pellucid, smooth, without any obvious 

 sculpture, inner duplicatures narrow; muscular spots rather in front of the middle, 



