KEY TO THE ENTOMOSTRACA OF COLORADO 27 1 



Number 



of 

 Species 



Genus Graptoleberis, p. 284 1 



Genus Leydigea, p. 284 i 



Genus Alona, p. 284 3 



Genus Dunhevedia, p. 285 i 



Genus Pleuroxus, p. 285 3 



Genus Alonella, p. 286 2 



Genus Chydorus, p. 287 i 



Sub-class Copepoda, p. 287 



Family Centropagidae, p. 288 



Genus Diaptomus, p. 288 13 



Family Cyclopidae, p. 294 



Genus Cyclops, p. 294 5 



Family Harpactidae, p. 296 



Genus Marshia, p. 296 i 



Genus Canthocamptus, p. 296 2 



Sub-class Ostracoda, p. 297 



Genus Candona, p. 297 i 



Genus Cyclocypris, p. 297 i 



Genus Cypria, p. 297 i 



Genus Cypridopsis, p. 297 2 



Genus Cyprinotus, p. 297 i 



Genus Cypris, p. 297 1 



Genus Erpetocypris, p. 297 1 



Genus Iliocypris, p. 297 i 



Total 81 



Key to the Entomostraca of Colorado 



1 (100, 139) Feet varying in number; usually foUaceous. Carapace usually 



present. Paired compound eyes usually present (in the Cladocera they are 

 fused to form a single median mass) . . Sub-class BRANCHIOPODA 2 



2 (.33) Post-cephalic appendages 10 or more. Animals usually of some size 



(6-40 mm. or more). 3 



In the sub-class Branchiopoda the three following orders — Anostraca, Notostraca, and Conchostraca — 

 are often classed together as a single order, Phyllopoda; and though they differ widely in appearance, because 

 of diverse development of the carapace, they are so much alike in general organization that they form a very 

 convenient group when combined. The appearance and structure of these animals are sufficiently illus- 

 trated in Figs. 2, s, g, and r^, and the number and nature of the appendages, in Table I. 



None of the Phyllopods are marine, though one species, Arlemia salina, lives in salt pools of very much 

 greater concentration than sea-water. Though some Phyllopods are found in permanent lakes, they belong 

 pre-eminently to transient pools, those which form in rainy weather and last, at most, for but a few weeks. 

 In this short time there mature, from eggs lying dormant in the dry earth, individuals which produce eggs that 



