110 Annals Entomological Society of America [Vol. IV, 



June 3rd. Collections of the nymphs were made June 12, 14, 

 and July 1. By July the nymphs were becoming scarce, 

 several cast skins were found on the dry stones of the shore, 

 after the last date, but no nymphs were seen. 



Measurements. 



Length of body Length of setae 



Male 5 m. m. 6 m. m. 



Female imago 4.5 m. m. 



Nymph 5 m. m. 1.2 m. m. 



Male imago. General color brown, paler on the legs and below. 

 Head, above, eyes very prominent, upper division reddish brown, lower 

 one darker. Front of head light, antennae light brownish; ocelli white, 

 the lateral ones with an inner lunate band of brown, the median one 

 with a complete ring of brown. Thorax, above yellowish shaded with 

 brown; mesonotum with its posterior margin edged with brown. Ridges 

 of the pleurae shaded with brown. Sternae pale with sub-quadrangular 

 areas of brown before the middle legs and a median shield of brown be- 

 hind them. Legs pale with a transverse band of brown at the distal 

 end of the femora; first tarsus of the foreleg but slightly longer than the 

 second; the third twice as long as the fourth. Wings hyaline, brownish 

 at the base. Abdomen, brownish above, pale below. Setae 3, pale, 

 the joinings of the basal segments ringed with brown. 



Female imago. Eyes small and distant showing the light colored 

 occiput between. Body more robust and abdomen slightly darker than 

 that of the male. Foreleg twice as long as that of the male. 



Nymph. Small with head and thorax rounded and the setae curv- 

 ing forward over the abdomen. General color a muddy yellow with 

 darker markings on the dorsal side, pale below. This species is easily 

 distinguished from Ephemcrella deficiens by its double median row of 

 spines on tergites 4-7 and by its generally lighter color. Head smooth, 

 (PL VI, fig. 5) ; antennae light brownish, first and second basal segments 

 edged with brown. Thorax, prothorax with a tubercle like elevation 

 on either side the median line. Legs (PI. VII, fig. 2) with the femora 

 rather stout and their hinder margins bordered with a row of stout hairs 

 sparsely distributed. Claws serrate (PL VII, fig. 2) with a chitinous 

 ridged plate on the underside of the tarsus (PL VII, fig. 2). Abdomen, 

 above, segments 5-6 pale marked with brown pencilings, other segments 

 brown with darker edges. A double row of irregularly triply dentate spines 

 extending over segments 4, 5, and 7. The lateral margins of segments 

 4-9 spinose with their posterior lateral angles becoming more acuminate 

 posteriorly. Gills present on segments 3-7; Elytroid lamella absent; 

 the superior lamella simple; the inferior fimbriate lamelliform. Abdo- 

 men, beneath, pale with a median row of distinct linear brown spots on 

 sternites 1-9. Setae, 3, sparsely beset with coarse hairs; color, pale with 

 a transverse band of brown across the center. 



