670 FRESH-WATER BIOLOGY 



28 (29) Post-genital region 8-segmented; cercopods ensiform. 



Euhranchipus serratus Forbes 1876. 

 Described from specimens taken in Illinois. 



29 (28) Post-genital region 9-segmented; cercopods dilated with obtuse 



apices Euhranchipus bundyi Forbes 1876. 



Described from specimens collected in Wisconsin. 



30 (17) Frontal appendage of male either vertical or extending out from the 



middle of front of head; terminal segment of copula tory 

 organ spiny 31 



31 (32) Post-genital segments distinct in both sexes, cyUndrical, cercopods 



always distinct Branchinella. 



Only one species in North America. . Branchinella gissleri Dadsiy 1910. 



This interesting phyllopod has been recently described 

 from specimens collected in New York. Packard ('83) 

 confused it with Euhranchipus holmanii (Ryder). The 

 male frontal appendages are usually twisted, and coiled 

 together. 



Fig. 1027. Branchinella gissleri. Dorsal view of head of male. 

 X 5- (After Daday.) 



32 (31) Post-genital segments fused in both sexes; cercopods confluent. 



Thamnocephalus . 

 Only one species Thamnocephalus platyurus Packard 1879. 



A peculiar species that has been recorded from Ellis, 

 Kansas, where it frequented temporary pools in the 

 bottoms of ravines, and from La Junta, Colorado, 

 where it w^as found in a "cattle pool." 

 Fig. 1028. Thamnocephalus platyurus. Dorsal view of 

 male. X i. (After Packard.) 



Z2> (6) Clasping antenna of male triarticulate. Family Streptocephalidae. 

 Only one genus in America Streptocephalus . . 34 



34 (35) Anterior digit of male clasping antenna broad, undulate, bifid at tip. 



Streptocephalus texanus Packard 187 1. 



The second antennae of the female scarcely exceed the first in length; 

 her cercopods are stouter than those of the male. 



The appendages beneath the head of the male are root-like and give the 

 animal a very pecuhar appearance. 



Texas, Kansas, Colorado, Nebraska. This species occurs in the spring or 

 fall in pools on the open prairie. 



Fig. io2g. Streptocephalus texanus. Head of male. X 4- (After Packard.) 



35 (34) Anterior digit of male clasping antenna nearly straight, hnear. 



Streptocephalus sealii Ryder 1879. 



New Jersey. This species has been known to appear twice in the same pool 

 during a summer, in June and August, following rains. 



Packard described another species, S. floridanus, but the description was 

 not definite enough to differentiate it from other American species. 



Fig. 1030. Streptocephalus sealii. Head of male. X 3- (After Packard.) 



