408 Wificonsin Academi/ of Sciences, Arts, and Letters. 



metrical, its distal end being expanded to the 



rights, Trybomt 



The endopodites are two-segmented, 

 Terminal spines of endopiodite fully as long as 



the endopodite, a large species, .stagnalis 



Terminal spines of endopodite short, a moder- 

 ate sized species, Eiseni 



The first antennae equal or exceed the length of the 

 whole body including the furca. 



The endoix)dite is rudimentary, ^ninutus 



The endopodite equals in length atout one-half the 

 first segment of the exopodite, 

 Fifth cephalothoracic segment with dorsal pro- 

 cess, endopodite one-segmented, saltillinus 



Fifth cephalothoracic segment with dorsal pro- 

 cess, endopodite ciommonly two-segmented, . . albuquerquensis 

 The endopodite exceeds in length one-half the first 

 segment of the exopodite, 

 The fifth cephalothoracic segment is armed with 



two dorsal processes, dorsalis 



The first segment of the abdomen has a prom- 

 inent swelling on the right side asymmetricus 



The endopodite equals or exceeds in length the first 

 segment of the exopodite. 

 There is a digitiform pi-ocess on the right pos- 

 terior border of the first abdominal segment. 

 This process is variable in length, typically, 

 in signicauda, extending far beyond the sec- 

 ond segment, signicauda, nudus. washing ioneyisis, Judayi 

 (These species can be satisfactorily separated 

 only by the characteristics of the male. Gen- 

 erally the abdominal process is much more pro- 

 nounced in signicauda. The lateral projec- 

 tions of the abdomen are strongest in Judayi, 

 less pronounced in nudus a'nd about equally 

 prominent in Washington ensis and signicauda). 

 The first abdominal segment bears no process on its 

 right hand posterior margin. 

 The lateral spines of the abdomen are either ab- 

 sent or very minute, 

 The exopodite is distinctly three-segmented. 

 Antennae equal to cephalothorax, a very 



large species, Shoshone 



Antennae reach to furca, Wardl 



The exopodite is two-segmented, the abdomen 

 elongated. 

 The abdomen is very much elongated, the 

 Lateral swelling of the first segment very 

 slight, tenuicaudatus 



