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A CONCISE GENERICAL SYNOPSIS, WITH AN ANNOTATED LIST, 

 OF THE SPECIES OF BRITISH EPHEMEEIDM. 



BY REV. A. E. EATON, M.A., F.E.S. 



Now that the final (6th) part of a " Revisional Monograph of 

 Recent Ephemeridce or Mayflies " has been published in the Transac- 

 tions of the Linnean Society of London, 2nd series, Zoology, vol. iii, 

 pp. 352, pis. 65 (1884—58), occasion may be taken to review the 

 nomenclature of the British species, so far as to show in what respects 

 it now differs from that which was adopted in the " Catalogue of 

 British Neuroptera " issued in the year 1870 by the Entomological 

 Society of London, and the "Monograph on the Ephemeridce' f in the 

 Transactions of the same Society for the year 1871. In these earlier 

 publications 37 British species, classed in ten genera, were admitted. 

 Of those reputed species two were spurious ; but the total number 

 has been maintained by the addition of two new species to our fauna. 

 The number of British genera has, however, been enlarged to thirteen 

 by the sub-division of two of the former ten along lines of separation 

 that were recognised to some extent tacitly in 1870. 



1. — Fifth tarsal joint from the tip of the ? fore-leg and of the hinder-legs of both 



sexes either wanting or distinguishable only by contour or colour 2. 



Fifth tarsal joint from the tip articulate with with the tibia in both sexes, and 



usually in all of the legs ; but when it is distinguishable by contour or colour 



alone, this joint is long 8. 



2. — Three caudal setse 3. 



Two setse, the third aborted. $ eyes bi-partite ; the upper segment turbinate. . . 7. 



3. — Four wings 4. 



Two wings, the hinder lacking. $ eyes smoothly contoured, far asunder... 



Ctenis. 



4. — <J eyes smoothly contoured 5. 



(J eyes more or less ascalaphoid (indistinctly so in Habrophlebia) 6. 



5. — Basal joint of $ forceps one of the shortest Ephemera. 



Basal joint of <J forceps much the longest Potamanthus. 



6. — Basal joint of $ forceps much longer than the remainder. Hind-wing slightly 



arched in front .. Leptophlebia. 



Basal joint of 3 forceps sub-equal in length to the remainder. Hind-wing an- 



gulated in the middle of the costa Habrophlebia. 



Basal joint of <J forceps very short ; 2nd joint much the longest. Hind-wing 



arched in front Ephemerella. 



7. — Hind-wings minute, moderately broad, obtuse, bi- or tri-nerved, and (as a rule) 



without a cross veinlet Baetis. 



Hind- wings minute, very narrow, binerved Centroptilum. 



Hind-wings lacking Cloeon. 



