90 



[September, 



The neuration of the fore- wings, and the proportions of the forci- 

 pal joints, are very similar to those of the last genus. But the eyes of 

 the are simple, and the central seta is rejected. The sides of the 

 dorsal arcus of the last well-formed segment of the abdomen are pro- 

 longed posteriorly so as to form an acute, more or less flattened, spine 

 on each side in all of the genera from Bcetisca to the present genus 

 inclusive. 



Genus Heptagenia, "Walsh. 

 Syn. Baetis, auct. part. 



Ecdyurus (misspelt Ecdyonurus) Etn. 

 Distrib.— N. Hemisphere ; and, according to M. Blanchard, Chili. 

 The principal difference between this genus and the preceding, in 

 the neuration of the wings, is that the first of the supplementary ribs 

 between the vas ulnare and vasa interna terminates at some distance 

 in advance of the angle of the wing, and supplies with veiulets no part 

 of the internal margin; that portion of the inner margin which is 

 included by the two supplementary ribs receiving upwards of four 

 supplementary veins and their veinlets. The first joint of the 3-jointed 

 forceps is the longest. Egg-valve entire. Central seta rejected. Eyes 

 entire in the male. 



Type H.flavescens, "Walsh. 



Distrib. — England, 4 sp. ; Germany, &c., N. America. 



Lobes of the penis divergent. "Wings of the sub-imago with the 

 cross- v^einlets not margined with a darker colour than that of the rest 

 of the wing, and of the same colour as the wing until shortly before the 

 last moult. 



Section B, H. venosa, Eab. 

 Syn. Ecdyurus, Etn. 



Distrib. — England, 3 sp. ; Europe, &c. 



Lobes of the penis slightly separated, horizontally flattened and 

 triangular. Cross-veinlets in the wings of the sub-imago conspicuously 

 margined with a darker colour, in most species. At the time when I 

 proposed the name Ecdyurus for this genus, I imagined that Mr. Walsh's 

 Heptagenia was a dismemberment of Falingenia, Burm. ; but he having 

 kindly forwarded to me, for the British Museum, types of his new genera, 

 I find that Heptagenia is the same as Baetis, Burm., Pict. 



Having now surveyed the genera, I will attempt to point out the 

 affinities presented by them one to another. The family seems to con- 



