42 NEW YORK STATE MUSEUM 



Among the other four North American nymphs described by 

 Eaton are two that will doubtless represent good and distinct 

 genera; and one of these I have been able to identify; for it I 

 erect the new genus DruneUa. The structural relations 

 between the American nymphs of the Ephemerella alli- 

 ance described by Eaton and those I have since obtained may be 

 set forth by means of the following key: 



a Antennae inserted in deep angular notches in the front margin of the 

 frons; dorsal hooks of abdomen wanting; nymph from Colorado, 

 imago unknown 1 

 aa Antennae inserted upon the upper surface of the frons; dorsal hooks 



hooks more or less developed in a double row upon the abdomen 

 6 Head armed with high occipital tubercles; hind wings visible at the 



sides below the fore wings D r u u e 1 1 a gen. nov. 



b& Head smooth above; hind wings visible on the dorsuiu between the 



bases of the fore wings 

 c Gill lamellae present on abdominal segments 3-7 



d Front femora strongly tul.eivulate on inner margin; lateral spines 

 of abdominal segments poorly developed, the abdominal margin 

 not serrate. Eaton's no. I from Washington 2 ; imago unknown 

 dd Front femora smooth on inner margin; lateral spines of abdom- 

 inal segments strongly developed 

 e Dorsal hooks of abdomen erect, high, strongly developed 



Ephemerella bispina sp. nov. 

 ee Dorsal hooks of abdomen slightly developed, hardly elevated 



above the surface. 1'nknown species from New York (p.45) 

 cc Gill lamellae present on abdominal segments 4-7 



d The operculate anterior lamella of the 4th segment covers suc- 

 ceeding lamellae but imperfectly, these successively protruding 

 their whole apical margins. Katon's no. IV; imago unknown 3 

 dd The operculate anterior lamella of the 4th abdominal segment 

 covers closely all succeeding lamellae, only their extreme 

 apical margins visible 



e Body hardly more than twice as long as wide; Ephemer- 

 ella sp? from Pecos N. Mex. 

 ee Body more than three times as long as wide 



Ephemerella excrucians 



Dnmella gen. nov. 4 



I have determined the nymph of this genus by means of the 

 venation of the developing wing. Professor Cockerell sent me 

 two nymphs from Pecos New Mexico, one of which, a male 



1 Eaton no. III. Monograph, p. 132, pl.39, 22 figs. 



"-Monograph, p.131, pl.38, figs. 1-10. 



'Monograph, p.133, pl.40, 17 figs. (Colorado) 



4 To my friend, Professor Theodore Dru Alison Cockerell. 



