MAY FLIES AND MIDGES OP NEW YORK 45 



This species differs in the nymphal stage from the nymph next 

 described, chiefly the presence of well-developed dorsal hooks and 

 the absence of black rings on the base of the setae. 



Ephemerella unicornis s'p. nov. 



Along with the six specimens ofE. bispina came a single 

 male of another apparently very distinct species, distinguished 

 at a glance from all the others by an erect conic tubercle upon the 

 front margin of the middle lobe of the mesothorax. This species 

 is notably smaller, measuring but 5 mm. in length, with the setae 

 of the same length and the wing hardly longer. The hind wing 

 also is marked with a more distinct basal costal angulation than 

 is common in this genus. The spines beside the backward pro- 

 longation of the middle lobe of the mesothorax are present also 

 in this species but apparently not so large. Unfortunately the 

 specimen, although perfect, is a subimago, and the mature colora- 

 tion can not be given; it will probably be brownish since in the 

 subimago it is greenish as in E . bispina. The abdominal 

 appendages are well enough developed to show that the end seg- 

 ment of the forceps will be much shorter than in E . bispina, 

 while the inner appendages will probably be of the same type as 

 in that species, though probably relatively shorter. 



Ephemerella sp?, near ignita 



This species occurs at Ithaca, but I have thence but a single 

 nymph. There are two nymphs in the U. S. National Museum 

 labeled " From stream on Mr Chamberlain's farm, Richfield 

 Springs, N. Y., May 13, 1837." It is very closely allied to the 

 European E . i g n i t a , as figured and described by Eaton 

 (Monograph, pl.40; whole figure copied in Cambridge Natural 

 History, vol.5, p.436, fig.282). 



One of the two nymphs from Richfield Springs is apparently 

 grown. It measures in length 8 mm., setae, 3.5 mm. additional. 

 Body rather more elongate than in the typical species; eyes lat- 

 erally prominent; abdomen (pl.10, fig.7) strongly depressed, the 

 usual submedian double row of dorsal tubercles scarcely indicated. 

 Lateral spines, thin, flat, sharp, on segments 4-9, a mere tooth on 

 4, increasing in size thereafter to segment 8, broader and less 

 sharp on 9. Gills present on segments 4-7, double, on 4 scarcely 



