KEY TO THE ENTOMOSTRACA OF COLORADO 



273 



8 (6, 7) Inner margin of basal segment of male clasping antenna with a promi- 

 nent spiny process at about the middle, and two short, finger-like processes 

 near base. Length: male, 16; female, 17. 2 mm. 



Branchinecta packardi Pearse 



La Junta (type locality), St. Vrain. Known only from plains of Colorado. 



Frontat or^an 

 ^Median eye 



^'Ist antenna 

 "Pa/red eyes 



^Zd antenna 



Fig. 4. — Branchinecta 

 packardi. Male. 



^Caudal sfylefs 



Fig. 5. — Branchinecta packardi. Female. 



(5) Head of male with one or two frontal processes. 



Family CniROCEPHALroAE 



Frontal process of male long and much branched. End of abdomen 



flattened in both sexes. Second joint of male clasping antenna curved and 



tusk-like. Female second antenna long and oar-like. Genus Thamnocephalus 



Only one species known. Length: male, 23; female, 26.5 mm. 



Thamnocephalus platyurus Packard 



Near Denver, La Junta. [Plains of Colorado and Kansas.] 



i orqan ^° (4) Clasping antenna of male 3-jointed and 

 much bent. 



\-Pwred eyes Family StREPTOCEPHALEDAE 



'^d"'"<'y^ Genus Slreplocephaltis 11 



/st antenna 



Zd atTTenno 

 Frontal process 



Fig. 6. — Thamnocephalus platyurus. Fig. 7. — Streptocephalus texanus. Fig. 8. — Streptocephalus 



Male. Male. cohradensts. Male. 



II (12) Distal digit of male clasping antenna flattened, undulate, and bifid 

 at the tip. Frontal process less than one-half first joint of antenna. Length: 

 male, 16.2; female, 14 mm. . . Streptocephalus texafius Fa.cksiid 



Denver, St. Vrain, Mesa de Maya. [Plains of Texas, Colorado, Kansas and Nebraska.] 



