MAY FLIES AND MIDGES OF NEW YORK 71 



toothed. The ventral plate, if viewed from the side, is in the 

 form of a strong claw with serrate margin; from beneath, its 

 margin is excised rather deeply, and each of the side lobes has 

 about three teeth. On cither side the apex of a blackish rod 

 is usually visible. The penis has the apex much dilated and 

 armed with two or three teeth. 



This species, which belongs to the same group as the European 

 O. f r i c i Klap., should be very easily recognized from the 

 ventral plate. 



10. Oxyethira viminalis, n. sp. 



The margin of the last dorsal segment is slightly and simply 

 excised. Beneath, the margins of the segment recede and form 

 a deep excision. The ventral plate has the margin nearly 

 straight, and above it are two blackish appendages no doubt 

 the homologues of the hooks which lie above the ventral plate 

 in several European forms. The penis is large, and with its 

 sheaths forms a very complicate structure; the apex, however, 

 is simple. The only other appendages visible are a pair of 

 lateral rods. 



Described with great hesitation from a single J 1 from Ithaca, 

 but after wards, fully verified from further material from Prof. 

 NVrdliam (Lake Forest, 15 Oct. 1902). 



11. Oxyethira dualis 



In this species the appendages are very simple; seen from 

 above the penultimate segment is deeply excised; from the same 

 point of view is visible a quadrate penis cover, the posterior 

 margin of which has two slight excisions. From beneath is 

 seen the simple ventral plate, almost straight in its posterior 

 outline, the hind angles slightly oblique; the plate is rather 

 broader at its base and on each lateral margin is a faint angle. 

 The apex of the penis has an elongate swollen part, probably 

 exaggerated in figs. 37 and 38, through the presence of some 

 extraneous matter; after preparation this part had the appear- 

 ance of having two slightly chitinized straight rods and a sickle- 

 shaped one. 



1 Las Vegas, New Mexico. (Cockerell.) 



