POTAMANTHUS. 51 



Hab. Puget Sound, Washington Territory. 

 I have examined one specimen, in alcohol. 

 I saw a species of Baetis from Mexico (in the Berlin Museum), 

 but the only specimen, a female, was very much mutilated. 



POTAMANTHUS Pictet. 



Three setos; wings four, transverse veins numerous; eyes, in the 

 male, double, large, approximate. 



1. P. cupidus. 



Ephemera cupida Say, Godman's West. Quart. Rep. II, 163, 1. 



^ Black ; thorax blackish-gray, a broad dorsal stripe and 

 each side an impressed line black ; eyes large fuscous ; abdomen 

 black, the segments having the posterior margin pale, a dorsal line 

 and each side an oblique obsolete line, whitish ; seta? longer than 

 the body ; feet pale fuscous, tarsi black, antei'ior feet black ; wings 

 obscure, posterior ones pale, at tip obscurer. 



9 Like the male, but the eyes are small, remote : the abdo- 

 men black, ventral incisures pale ; setaj a little longer than the 

 body. 



Length of body, ^^ 11, 9 8 millim. Length of seta3, ^^ 5, 9 

 10 millim. 



Hab. Cincinnati, Ohio ; 15th of May. Common (Say). 



The form of the eyes demonstrates Mr. Say to have wrongly 

 determined the sexes; therefore I have changed his female to male 

 and his male to female. It will be observed that the length of 

 the setse given by Mr. Say disagrees with his description. 



2. P. concinnus ! 



Palingenia concinna Walk.! Catal. 553, 17. (^ Imago.) Palingenia 

 pallipes Walk.! Catal. 553, 16. ( 9 Imago and subimago.) Baetis 

 tessellata Walk.! Catal. 566, 32. ( f Subimago.) 



J* Imago. Pitchy black; beneath partly ferruginous; antenna? 

 black ; setse double the length of the body ; intermediate one 

 much shorter, luteous, incisures black ; feet luteous, tarsi fuscous, 

 anterior feet entirely piceous ; wings hyaline, veins luteous, the 

 aipical veins much obscurer ; costal margin of the anterior wings 

 fuscous at the apex. 



9 Imago. Obscure ferruginous, beneath paler ; disk of the 



