THE CANADIAN ENTOMOLOGIST. 81 



as they indicate general distribution of the deeper pigmentation 

 areas. What is described from pickled or mummified specimens 

 as yellow may have been green in life. 



This genus includes species \'arying from 10 mm. to 20 mm. 

 in length, and from 18 mm. to 50 mm. in expanse of wings. It is 

 characterized by the possession of but two ocelli, by having a 

 Ijroadly depressed body, short head retracted under the front of 

 a wide prothorax, long antenna^, and very short caudal filaments 

 that are often hardly longer than the abdomen is wide. The 

 venation of the wings is characterized by numerous costal cross- 

 veins, a short sub-costal vein, not reaching the level of the cord, 

 and the branches of the vein Cu 1 appear to spring from its anterior 

 side. 



Nymphs of this genus, so far as observed hitherto, live in 

 spring-fed rivulets under stones. About Ithaca, N. Y., they are 

 not uncommon in such places, and they are abundant in a small 

 southern tributary to Enfield Creek near the mouth of the gorge. 

 The nymphs are unique in form, having a wide thorax, broadly 

 rounded and covered with an appressed pubescence above. The 

 abdomen is narrower and rather short. A few long tapering gill 

 filaments protrude backward singly about the base of the legs, 

 both dorsally and ventrally. 



Nine species are here described, of which seven are believed 

 to be new. Only the adults are characterized, and, unfortunately, 

 but one sex is known as yet in the case of several of the species. 

 The accompanying plate will doubless serve better than the de- 

 scriptions for distinguishing the species. The drawings of genitalia 

 and of the disc of the prothorax have all been done on uniform 

 scale. They are the work of the junior author. 



Two very distinct types of male genitalia occur in this genus. 

 One is represented only by a new species from Nevada, Peltoperla 

 thyra. In this, the 9th abdominal segment is abbreviated almost 

 to complete disappearance on the mid-dorsal line; the mid-ventral 

 callosity is a mere crescentric transverse ridge at the base of a 

 deep V-shaped suture, the supra-anal plate is remarkably hyper- 

 trophied, elevated, bent forward in the middle, and armed with 

 a pair of lateral expansions beside its knobbed tip (Fig. 14). In 

 the other group, represented by all the other species of which 



