372 PROCEEDINGS OF THE ACADEMY OF 



cross-veins moderate, subequal, pale greenish hyaline, except the basal third of 

 the three costal veins, and occasionally their tips, which are fuscous ; in the 

 hind wings they are all immaculate. 



The 9 differs from <J* as follows: The general color is paler; the thorax is 

 generally almost yellow ; the abdomen ferruginous, each joint generally darker 

 at tip ; and the wing-veins are dusky along the costa and at the tip of the wing, 

 gradually becoming hyaline as they approach the postcostal angle. 

 ' Length tf 4 5 mill. ; 9 57 mill. Alar exp. $ 1415 mill. ; 9 1516 

 mill. Seta tf 1314 mill. ; 9 8 11J mill. Anterior leg $ 7 mill. ; 9 (same 

 size) 5 mill. Eight $, eight 9- The diagnosis of dcbilis is so brief that it is 

 scarcely sufficient. 



The (^ subimago differs from the imago in the general color being obscure ; 

 the thorax is almost yellowish, and the abdomen obscure piceous or ferruginous, 

 immaculate; the anterior tarsi are fuscous; the abdominal seta cloudy at tip 

 and pilose under the lens ; the wings are fumose, the veins and cross-veins 

 fuscous, the former rather coarse, the latter moderate; and the fringe on the 

 posterior edge of the wings is long and dense. 



Length tf 4| 5k mill. Alar exp. <^ 13 15 mill. Seta tf about 5 mill. 

 Anterior leg tf (same size as ^ imago) 5 mill. Two <$ ; 9 unknown. 



POTAMANTHUS. 



Potamanthus cupidus, Say. Undescribed imago. ^ Piceous, highly pol- 

 ished ; venter, except the penultimate joint, ferruginous ; anal processes pale ; 

 setae whitish, with fuscous incisures alternately wide and narrow on the basal 

 half, uniform behind the middle, and towards the tip becoming very wide. 

 Anterior legs brown, darker at the knees and the tips of the tibise ; four hind 

 legs pale yellowish brown, immaculate. Wings hyalioe, veins rather coarse, 

 especially on the costa, cross-veins fine, the former fuscous, except on the 

 postcosta, where they are hyaline ; the latter hyaline, except at the subcostal 

 tip of the front wing, where they are fuscous. 



Length tf 7J mill. Alar expanse $ 18 mill. Setae <JH8J mill.; intermediate 

 seta about 16 mill. Anterior leg tf 8 mill. One $ ; 9 unknown. 



The subimago, which alone was known to Say, and from which, after several 

 unsuccessful attempts, I finally succeeded in breeding the $ imago, occurs 

 rather abundantly on rafts of Wisconsin pine-logs from the middle of May to 

 the middle of June, unaccompanied, so far as I could discover, by the imago. 

 The " two divergent, abbreviated, obsolete, whitish lines" which Say mentions 

 as peculiar to the $ (= 9 a P u d Say) I noticed only in a single 9 > an d they 

 disappear in death. 



Length J 1 7 9 mill. ; 9 9 mill. Alar exp. ^ 20 26 mill. ; 9 19 24 mill. 

 Setae tf 1114 mill.; intermediate seta ^ 912 mill. Setfe 9 8 11| mill. ; 

 intermediate seta 9 8 10 mill. Ant. leg. $ 8 mill. ; 9 (same size) 7 mill. 

 Eleven tf, three $>. 



Potamanthus? odonatds, n. sp. Piceous; sex uncertain; head, anterior legs 

 and abdomen deficient. Posterior ltgs pale ferruginous, tips of tarsi cloudy. 

 Wings hyaline; veins moderate, fuscous ; paler towards base; cross-veins fine, 

 fuscous at terminal half, hyaline at basal half; terminal one-third of anterior 

 wing dusky, with a definite outline. 



Alar expanse 25 mill. I have referred this fragmentary specimen, which I 

 found drowned in a pool of water, to Potamanthus, because it agrees with that 

 genus in its tarsal structure (which is the same as that of Batis, subgenus C,) 

 and also in its peculiar neuration, viz. : four veins on the postcosta, the an- 

 terior one much curved, and emitting anteriorly from its centre a bifurcate vein. 

 I am not aware that there are any other examples in Ephemerina of the style of 

 ornamentation, so characteristic of the Odonata, which prevails in the wings 

 of this species. 



[Sept. 



