1868.] 



86 



The neuration of the anterior wings is somewhat like that of the 

 preceding genus ; the vasa interna, however, are connected together by 

 a larger number of cross-veinlets. Forceps of three-jointed ; their 

 basal joints much the longest. $ with the central seta rudimental, 

 not well developed, as in Polymitarcys. 



Genus Pentaqenia, Walsh. 

 Syn. Falingenia, Subgen. A., Walsh, 1862. 

 Type P. vittigera^ Walsh. 



The first ulnar rib is bipartite ; its bipartite anterior, and its bifid 

 posterior, veins, both include a simple supplementary vein in their forks, 

 and the one in addition includes two or three supplementary veinlets. 

 The simple posterior ulnar rib is met not far from its origin by a simple 

 supplementary vein, which is suddenly curved forwards towards the 

 point of contact (as in Ephemera). The very convex outermost veinlet 

 from the recurrent vein of the third vas internum, which is succeeded by 

 some very irregular, feeble veinlets, is distinctive of this genus. Forceps 

 of four-jointed, their second joints the longest. 



G-enus Hexagenia, Walsh. 

 Syn. Falingenia, p., Pictet ; Idem subgenus B., Walsh, 1862. 

 Type H. limhata, Guer. 

 Distrib. — Arctic America, Canada, United States, and the Amazons. 

 The most obvious differences between the neuration of the anterior 

 wings of Hexagenia and Ephemera are the excess in number of the 

 more or less crowded, parallel, straight, veinlets extending from the 

 third vas internum perpendicularly to the internal margin, over those 

 which unite it and the second supplementary rib. The recurrent 

 vein of the third vas internum gives off several nearly straight 

 parallel veins. The ^ has the second joints of the four-jointed forceps 

 the longest, and both sexes reject the central seta. 



Genus Ephemera, De Geer. 



Syn. Ephemera, Liu., part. 



Type E. vulgata, Lin. 



Distrib. — Europe; N. China, Hindostan, Ceylon (aberrant); 

 Canada, Illinois. 



The forceps of Ephemera are similar to those of Hexagenia, but 

 the central seta is sub-equal to the others. The cross-veinlets between 



