282 



UNIVERSITY OF COLORADO STUDIES 



63 (64) Dorsal margin of valves with short, backwardly directed tooth about 



middle. Intestine convoluted Genus Depanothrix 



Only one species in America. Length, 0.7 mm. 



Depanothrix deniaia (Euren) 



Twin Lakes; 9,200 ft. [Michigan, Minnesota, Wisconsin. Europe, except southern portion.] 



Fig. 37, — Depanothrix dentata. (Afte; 

 Lilljeborg.) 



Fig. 38. — Streblocerus serricauda- 

 tus. (After Birge.) 



64 (63) Dorsal margin of valves smooth 65 



65 (66) Antennules sharply bent near the end. Intestine convoluted. 



Genus Streblocerus 



One species in Colorado. Pre-anal part of post-abdomen with serrate 



dorsal margin. Length, 0.5 mm. . . Streblocerus serricaudatus (Fischer) 



Tolland; 9,600 ft. IWidespread but rare in United States. In Europe except extreme north.] 



66 (65) Antennules not bent. Intestine not convoluted. 



Genus Macrothrix 67 



67 (68) Conspicuous folds on dorsal surface between head and body. Length, 

 o. s mm Macrothrix montana Birge 



Pikes peak; 11,000 ft. [California and Colorado.] 



Fig. 39. — Macrothrix montana. 

 (After Birge.) 



Fig. 40. — Macrothrix Fig. 41. — Macrothrix hirsuticornis. 

 montana. Post-abdomen. 

 (After Birge.) 



68 (67) No dorsal folds. Post-abdomen bilobed. Antennules with about 6 

 rows of hairs on anterior side. Length, o. 5 mm. 



Macrothrix hirsuticornis N. and B. 



Boulder, Tolland, Twin Lakes region; 5,400-12,000 ft. [Colorado, Rhode Island. Greenland, Spitz- 

 bergen, Northern Eiuope to Africa.] 



