EEV. A. E. EATON OX RECENT EPHEMEEID.E Oil MAYFLIES. 19 



Burmeister, in 1839, l»sed his arrangement of the genera primarily upon the compara- 

 tive scarcity or abundance of cross veiulets in the wings, and employed as secondary 

 characters the conditions of the oculi, ocelli, tarsi, and setse. He, too, renamed the 

 genus Bracliycercns of Curtis, calling it Oxijcypha. Merging Leach's Cloeon and Baetis 

 together vinder the shorter form of the first name (C'loe) he regarded them as mere 

 sections of this. The appellation Baetis was misapplied by him, the first of the two series 

 of species designated by it being equivalent to the unrestricted Potamanthus of Pictet 

 (probably his materials were dried specimens defective in setoe), the second series (with 

 one exception) to Heptagenia. He founded a new genus {Ballngenia) for the reception 

 of some species of the comprehensive Ephemera of early authors, distinguished by their 

 possessing a distinct median ocellus and four-jointed tarsi, in lieu of an obsolescent 

 median ocellus and tarsi almost five-jointed (the fifth or basal joint being intimately 

 adnate to the tibia and ill-defined). These genera were arranged by him in the same 

 sequence as that in which they are mentioned in this paragraph. 



Professor Westwood, in 1840, established a genus Leptophlehla for some small species 

 of the " Ephemera cauda triseta " series of early authors, and unknowingly revived the real 

 genus Baetis of Leach, under the name Braclnjiildehia. From allusions to Burmeister's 

 genera in the Addenda to the Generical Synopsis, he appears to have become acquainted 

 with the ' Handbuch ' while the ' Introduction ' was in the press, too late for a place to be 

 assigned to Puliucjeiiia. From consideration of the number of the wings and seta?, and 

 the structure of the nymph, he drew up the following arrangement of the genera : — 

 Ephemera, Leptophlehla, % Baetis (= Heptayenia), Ccenis, Cloeod, and BrachijphJehia. 



The scheme propounded by Pictet (1843-5) was constructed to a large extent with 

 reference to the abundance or the paucity of cross veiulets in the anterior wings, the 

 condition of the oculi in the male, and the number or tbe relative proportions of the 

 caudal setre. In the main the order of succession deduced from these data agrees with 

 that which is arrived at Avhen the genera are grouped according to the general habit of 

 their nymphs (so far, at least, as he had been able to ascertain this), viz. : — Burrowing 

 nymphs, creeping nymphs, and nymphs that swim with agility. The sequence of the ^ 

 genera is : — Ei>heia.era, Balingenia (= Bolymitarcys, Hexagenia, Campsurus, and the 

 restricted Palingenia), % Baetis (= Ueptagenia, and a species of Atalophlehia), Pota- 

 manthus {= the restricted Potamanthus, LeptoiMebia, Kabrophleltia, and Ephemerella), 

 Clo'e (= Baetis, Centroptilum, Callibcetis, and Cloeon), Ccenis, and Oligonenria. Pictet 

 foresaw that some of the species referred by him to the genera Palingenia and Pota- 

 manthus Avould probably prove to be incongruous, but was precluded by lack of materials 

 from verifying his suspicions. He also surmised correctly that the neuratiou of the 

 anterior wings in detail would furnish characters towards their discrimination, adding: — 

 *' Mais j'ai repugne a entrer pour cela dans une analyse aride, longue et minuticuse ; j'ai 

 craint de rendre plus diflicile encore riutelligence des descriptions;" but he did not attach 

 much importance to the tarsal characters. If he had known of the name of LeptophJehia 

 in time he would have used it instead of Potamanthus, although, as he remarks, this last 

 is more comprehensive in its application than the former. 



In 18G2 an account of some Illinois species of Ephemerida? was published by the late 



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