THE FAUNA OF BOULDER COUNTY, 

 COLORADO. II. 1 



By T. D. A. Cockerell 



Class CRUSTACEA Lamarck 

 Subclass ENTOMOSTRACA Miiller 



Size small or moderate; number of body-segments differing greatly in different 

 groups; young (except in many Cladocera and Ostracoda) appearing as unseg- 

 mented larvae with two or three pairs of appendages, of which two are constantly 

 biramose (Nauplius larvae). For a list of Colorado Entomostraca, see G. S. 

 Dodds, Univ. of Colo. Studies, V, pp. 243-250. 



Order BRANCHIOPODA 

 Suborder Phyllopoda Latreille 



Relatively large animals, with at least ten pairs of legs, often many more; antennae 

 usually small, not used for swimming. 



Family BRANCHIPODIDAE Fischer 

 Carapace rudimentary; eyes stalked; the second antennae flat and un jointed in 

 the female, jointed and prehensile in the male (Weldon). The following key to the 

 genera is mainly based on that of Weldon: 



1. Posterior abdominal segments united with telson to form a fin, deeply notched 

 apically, and with setose margins; head of male with a branched median 

 process ("frontal shrub" of Packard); second antennae of female oar-like 

 (subfamily Thamnocephalinae Packard) . . . Thamnocephalus Packard. 

 Posterior abdominal segments not thus modified 2. 



2. Anal lobes small or none, sparsely or not at all setose; abdominal segments 

 five or fewer, and a telson (terminal piece) (subfamily Artemiinae) 



Artemia Leach (Utah). 

 Anal lobes well-formed, their margins setose; abdomen of six well-formed 

 segments and a telson (subfamily Branchipodinae Packard) . . .3. 



3. Second antennae of male without lateral appendages; ovisac of female 



elongated Branchinecta Verrill. 



Second antennae of male apparently three-jointed, the last joint bifid or trifid; 

 first joint with a curved appendage . . . Slreptocephalus W. Baird. 



^Publication of the Colorado Biological Survey, No. 6. In this and subsequent parts the fauna of Tolland 

 will be included with that of Boulder County. Species which have been found on the University campus are 

 marked with an asterisk (*). 



Part I was issued in Vol. VILt, No. 4, of these Studies, under date of June, ign. 

 41 



