No. 43 3. J UNKNOWN EPHEMERID NYMPHS. 3 1 



former case; the margins of the joints more conspicuously 

 spined, particularly those of the abdomen, which increase in 

 size laterally, the last one forming a decided spur at the 

 posterior-lateral angle of the segment ; gill veins somewhat 

 stouter, and gills with a much more decided basal lobe. Col- 

 lected on the afternoon of June 14. During the night "four 

 subimagos emerged, and the next afternoon the only living 

 one molted to the imago stage. 

 Passaic, New Jersey. 



