356 CBVSTACEA 



Key to the genera of Cytlieridae here described: 



Oi Animals marine. 



61 Dorsal and ventral margins of shell uot'i)arallel 1. Loxoconcha 



62 Margins of shell nearly parallel. 



Cy Surface of shell rough 2. Cythereis 



Co Surface of shell smooth 3. Pseudocytheretta 



O2 Fresh-water animals. 



&i Animals free-swimming 4. Limnicythere 



62 Animals parasitic 5. Entocytiiere 



1. Loxoconcha Sars. Shell with a notch at the dorso-posterior 

 angle; ends and ventral margin extended into a flattened rim; first 

 antennae 6-jointed, with a group of slender setae on the last joint; sec- 

 ond antennae 4-jointed : 2 American species; marine. 



L. impressa (Baird) (Fig. 562). Length .82 mm.; height .51 mm.; 

 Vineyard Sound; very common in shallow water, among eel grass, 

 hydroids, etc. 



2. Cythereis Sars. Shell strongly calcareous; first antennae 5 or 

 6-jointed; second antennae 4-jointed, with a short flagellum in the female; 

 first pair of feet differing on the two sides of the body in the male : 10 

 American species; marine. 



C. arenicola Cushman (Fig. 563). Shell quadrangular, the dorsal 

 and ventral margins being almost parallel, 1 mm. long; ,5 mm. high; sur- 

 face with irregular patches, usually each with a single hair : common on 

 sandy bottoms in Vineyard Sound. 



Pig. 562 Fig. 563 Fig. 564 



Fig. 562 — Loxoconcha impreftsa (Cushman). Fig. 563 — Cythereis arenicola (Cush- 

 man), Fig. 564 — Pseudocytheretta edwardsi (Cushman). 



3. Pseudocytheretta Cushman. Inner border of shell irregular; 

 flagellum of second antennae 3-jointed; first foot of male with a seta on 

 the hinder border; left and right first feet of male very different: 1 

 species. 



P. edwardsi Cushman (Fig. 564). Dorsal and ventral margins of 

 shell nearly parallel, with rounded hairy ends; length 1.2 mm.; width 

 .61 mm. : Vineyard Sound in rather deep water, the commonest ostracod 

 of the region. 



4. Limnicyther'e Brady. First antennae 5-jointed with short bris- 

 tles on the outer edge; second antennae 4-jointed; mandible witli large 

 branchial plate: 2 American species, both in Illinois. 



