North American Fresh-water Ostracoda. 429 



ANALYTICAL KEY TO THE GENERA OF CYPKIDID.E.* 



1 (13). Second pair of feet ending in a cylindrical seg- 

 ment with two backwardly directed seta3. 



2 (3). Second pair of feet in both male and female six- 

 segmented. Second pair of maxillse without a branchi- 

 al plate. I. NOTODKOMAS. 



3 (2). Second pair of feet in female five-segmented, in 

 male six-segmented. 



4 (7, 8) Branchial plate of second pair of maxillae rudi- 

 mentary, in the form of two feathered setae. 



5 (6). Eye present. VIII. Candona. 



6 (5). Eye absent. IX. Typhlocypris. 



7 (4, 8). Branchial plate of second pair of maxillae 

 developed, in the form of three feathered setae. 



X. Candonopsis. 



8 (4, 7). Branchial plate of second maxillae with six 

 feathered setae. 



9 (10). Palp of second maxillae rudimentary. 



XI. Ilyocypris. 



10 (9). Palp of second maxillae normally developed. 



11 (12). Terminal segment of second pair of feet one 

 fourth as long as fourth segment. XII. Cypria. 



12 (11). Terminal segment of second pair of feet two 

 thirds as long as fourth segment. II. Cyclocypris. 



13 (1). Second pair of feet ending in a beak-shaped 

 segment with one backwardly directed claw. 



14 (15, 16). Caudal rami rudimentary, flagellum-like. 



XIII. Cypridopsls. 



15 (14, 16). Caudal rami somewhat rudimentary, small, 

 lamellar, terminating in a long seta, and having a 

 much shorter one, placed dorsally at some distance 

 from the tip. XIV. Potamocypris. 



16 (14, 15). Caudal rami cylindrical, ending in two claws. 



*A modiflcation of Vavra's Key (6**, p. 31). 



