46 UNIVERSITY OF COLORADO STUDIES 



(143) Pleuroxus W. Baird. Dodds says that Pleuroxus occurs abundantly in collections 



from several lakes about Boulder; no two individuals are alike, and he was unable 

 to determine the species. P. procurvatus Birge is reported from Pike's Peak and 

 Twin Lakes. 



(144) Dunhevidia King. D. seliger (Birge), near Boulder (Dodds). 



(145) Chydorus Leach. C. sphaericus (O. F. Muller). Boulder and Redrock Lake 

 (Dodds). Birge {Trans. Wise. Acad. Sci., 1909, p. 1051) remarks that the species of 

 Chydorinae are readily distinguishable, but the genera are in many cases ill-defined, 

 and in some cases seem to be indefinable. Thus Chydorus and Pleuroxus, widely 

 separated in the above table (mainly from Weldon), he considers hardly separable. 

 Camptocercus is an extreme type of the Alonopsis group. Dunhevedia is not so 

 near to Alona as is Graptoleberis. 



Order COPEPODA 



Small Crustacea, composed typically of about sixteen segments, in which the 

 biramous type of limb predominates; they are devoid of a carapace; paired com- 

 pound eyes are absent, except in Branchiura, the adult retaining the simple eye 

 of the Nauplius (Geoffrey Smith). This does not well apply to the Branchiura 

 (Argulidae) which are parasitic on fish. These animals become quite large (Argulus 

 caiostomi Dana and Herrick, found on suckers, 1 2 mm. long) and have the cephalo- 

 thorax developed into a broad lobed shield or carapace. The anterior maxillipeds 

 in Argulus are transformed into large sucking disks. 



Suborder Gymnoplea 



The division between the front and hind part of the body falls immediately in 

 front of the genital openings and behind the fifth thoracic feet; the latter in the 

 male are modified into an asymmetrical copulatory organ (Geoffrey Smith). 



Family CENTROPAGIDAE 



Cephalothorax distinctly separated from abdomen; first antennae long and com- 

 posed of 24-25 segments; female with only one egg-sac. 



(146) Diaptomus Westwood. Inner branch of first pair of legs two-jointed; of the 

 following three pairs three-jointed. D. signicauda Lilljeborg, near Boulder (Juday) 

 and Boulder Lake (C. F. Baker); D. leptopus var. piscinae Forbes,* University 

 campus (Marsh) and Redrock Lake (Dodds); D. nudus Marsh, Boulder (Dodds); 

 D. coloradensis Marsh, Corona and Tolland (Marsh). D. shoshone Forbes, 

 Tolland (Marsh in litt.). Eight other species of Diaptomus are reported from 

 Colorado by Marsh. 



Suborder Podoplea 



The boundary between the fore and hind parts of the body falls in front of the fifth 

 thoracic segment; the appendages of the fifth thoracic pair in the male are never 

 modified as copulatory organs (Geoffrey Smith). 



Superfamily CYCLOPOLDEA (Ampharthrandria) 

 First antennae of male differing greatly from those of female, being often genicu- 

 lated and acting as prehensile organs (Geoffrey Smith). 



