North American Fresh-water Ostracoda. 445 



Caudal rami (Fig. 1) slender, slightly bent, the dorsal 

 edge serrate for two thirds its length, sixteen to eigliteen 

 times as long as wide. Terminal claw nearly straight, 

 lightly toothed, half as long as the ramus. Terminal 

 seta half as long as the terminal claw, which is one and 

 a third times as long as the subterminal one; dorsal 

 seta two thirds the length of terminal one, and width 

 of ramus from subterminal claw. 



The "organ of Zenker" presents an unusually spiny 

 appearance (Fig. 3), since the spines are thickly set over 

 the entire surface of the cylinder instead of being in 

 wreaths, as is commonly the case; organ fully five times 

 as long as wide. 



Described from a number of specimens in the collection 

 of the Illinois State Laboratory of Natural History, 

 which were taken from a pond in the woods near Bloom- 

 ington. 111., April 22, 1879. 



V. Cypricercus Saes. 



1895. Oypricercus, Sars (58 p. 37). 



Natatory setae of both pairs of antennae well developed; 

 palp and masticatory lobe of the first maxillae narrow. 

 Feet as in the genus C^'pris. 



^ Caudal rami excessively developed and elongate, afford- 

 ing a ready means of recognition. Coecal appendage of 

 intestine unusually short; ovarial tubes much elongated. 



This genus has but recently been established by Sars 

 (57) to receive a South African form with excessively de- 

 veloped caudal rami. No species have been reported 

 as yet from America. 



VI. Erpetocypris Brady & Norman. 



1792. Cypris, O. F. Muller (49, p. 48). 



1820. Monoiilus, Jurine (36, p. 170). 



1889. Sri etocypris, Brady & Norman (9, p. 8*;. 



Second pair of antennae five-segmented. Natatory setae 

 of the third segment very short, not nearly reaching the 

 tips of the terminal claws and not plu.nose. Having no 



