20 EEV. A. E. EATON ON EECENT EPHEMEEID^ OE MAYFLIES. 



Mr. B. D. Walsh. The classification of the genera was determined by an application of 

 almost the same principles as were adopted by Burmeister, and is as follows : — J Ba'etis, 

 comprising three sections (Sect. A = Siphlurus ; Sect. B = Chirotonetes ; Sect. C = Bhi- 

 tlirogena) ; Fotamantlms (= Blasturus) ; FaUngenia with three sections (named by him 

 in the following year : A, Pentagenia ; B, Hexagenia ; C, Reptagenia) ; Ephemera, 

 Ephemerella, Bcetisca; Clo'e containing three sections (A = CaUibcetis ; B = species of 

 Callihcetis and Baetis ; C = Cloeoii) ; and Ccenis. 



Dr. Hagen, in 1863, used Pictet's genera in a revised order, alluding only incidentally 

 to forms foreign to Great Britain : — Oligoneuriu, Cceiiis, PaUngenia, Ephemera, Pota- 

 manthus, % Baetis, and Cloeoii (= Cloe). 



In 1868 a systematic catalogue of genera with named types, and with notes on their 

 geographical distribution, was published by me in the 'Entomologist's Monthly Magazine.' 

 My attempts to describe the wings in an intelligible manner, in the absence of illustra- 

 tions, were, to say the least, abortive. The genera stood thus : — Ccenis, Tricorythus, Oli- 

 gonetiria (with three sections), Campsurns (with two unreal sections), Polymitarcys, 

 PaUngenia, Pentagenia, Hexagenia, Ephemera, Poto^nanthus, Leptophlehia (with two 

 sections), Bcetisca, Colohurus, Siphlurus, and Reptagenia (with two sections). 



In the same year, while describing the nymph of Cainis, I adduced reasons for trans- 

 ferring this genus from the position near Baetis and Clo'eon, assigned to it by Pictet (on 

 account of the simplicity of its wing-neuration), to the neighbourhood of Leptophlehia, 

 series 2 (= Rabrophlehia), and likewise for the removal of Oligoneuriu, ranked next after 

 Ccenis by Pictet, to the vicinage of PaUngenia, changes that were carried out in my 

 work on the Ephemeridne in 1871, when a few minor alterations involving no principle 

 in the successiou of genera were also made. 



The structure of the tracheal branchiae of the nymph was taken as the basis of classi- 

 fication of Ephemeridae by Dr. A. Vayssi^re in his ' Thesis ' presented to the Paculte des 

 Sciences de Paris, and published in the ' Annales des Sciences Naturelles ' in 1882. He 

 arranged the genera in five groups : — 1, those having fringed branchial laminae, Lepto- 

 phlehia (= Hahrophlebia), Ephemera, Potamanthus, and Polymitarcys ; 2, those with 

 laminae devoid of fringes, Oniscigaster, Cloeopsis (= Cloeon), % Cloeon (= — — ?), f Cen- 

 troptihim (= Baetis); 3, those with simple laminae furnished at the base with either a 

 tuft of fibrils, Reptagenia (= Ecdyurus), Oligonetiria, Jolia, or a bifid appendage bearing- 

 very delicate imbricated lamellae, Ephemerella ; 4, those whose second jjair of brauchia 

 afford protection to the following pairs, Tricorythus and Ccenis; 5, "les larves dont 

 I'appareil respiratoire est completement cache ct protege par des jirolongements mesotho- 

 raciques dans I'epaisseur desquels naitront j)lus tard les ailes superieures," Bcetisca and 

 Prosopistoma. I examined and named the type specimens of this Thesis at Avignon in 

 August 1880 ; but the indications affixed to the phials appear to have become confused. 

 To the best of my recollection the specimens representing % Cloeon were junior examples 

 of something which I suspected might be Centrojytilum or Ba'etis ; but I did not ascertain 

 which. 



The additional knowledge of Ephemeridas gained since 1871 has not yet necessitated 

 any material departure from the sequence of the genera which I adopted. A few minor 



