28o 



UNIVERSITY OF COLORADO STUDIES 



47 (46) Head helmeted; eye remote from margin of head. Size and form 

 of helmet exceedingly variable. Often con- 

 sidered a variety of longispina. Length, 

 I . s mm. . . Daphnia hyalina Leydig 



Boulder, Twin Lakes; 5,200-9,200 ft. [Widespread in 

 Old and New Worlds.] 

 Fig. 29— Daphnia hyalina. ^g (^j) jj^ gjj^j.p gpjjjg ^j ^ppg^ posterior 



angle of shell 49 



49 (so) A sharp, backwardly directed spine at lower posterior margin of each 



valve Genus Scapholeberis 



One species with us. Length i . o mm. 



Scapholeberis mucronata (O.F.M.) 



Greeley, Boulder, Tolland, Twin Lakes; 4,600-9,600 ft. ICommon in America and in Old World from 

 arctic to tropical regions.] 



Fig. 30. — Scapholeberis mucronata. 



Fig. 31. — Simocepholus vetulus. 



Fig. 32. — Simo- 

 cephalus serrulatus, 

 (After Birge.) 



50 (49) Lower posterior margin of valves rounded. Blunt spine or angle 

 at upper posterior margin. Beak obscure. . Genus Simocephalus 51 



51 (52) Head rounded in front of eye. Length up to 3 . o mm. 



Simocephalus vetulus (O.F.M.) 



La Junta, Boulder, Greeley, Tolland, Twin Lakes region. In weedy margins of lakes and ponds. [Com- 

 mon in Eastern and Western Hemispheres from northern to southern portions.] 



52 (si) Head with spiny angle in front of eye. Length, 3 . o mm. 



Simocephalus serrulatus (Koch) 



Pikes Peak; 11,000 ft. Doubtful record from plains near Boulder. [General distribution about the 

 same as vetulus.] 



53 (40) Head not beaked; separated from body by depression above. . 54 

 (S7) Head small and depressed; eye large. Antennules small. 



Genus Ceriodaphnia 55 

 (s6) Abdominal claw with pecten. Hexagonal markings of shell with 

 simple contours. Head not inflated in front of antennules. Length, i . 4 mm. 



Ceriodaphnia reticulata Jurine 



La Junta, Boulder, Greeley, Tolland, Pikes Peak; 4,100-11,185 ft. [Widespread in America and from 

 northern Europe to Africa.] 



54 



SS 



