142 EEV. A. E. EATON ON EECENT EPHEMERID.E OE MAYFLIES. 



placed as in Tricorytlms maximus, and of a very similar character, but the laminae of the 

 hinder pairs are more rounded in form, and are not provided with an appendage on their 

 under surface. Moreover the elytroid pair are beset with short pubescence on the upper 

 surface, and ciliated with fine hair along their lateral and posterior borders ; the pairs 

 succeeding them are membranaceous, and their fringes are subdivided more sparingly 

 than in Tricorythus, the fibrils of the costal border and of the proximal portion of the 

 inner border of each lamina being simple or only bipartite, instead of pectinate, and 

 those of the distal margin having only two or three short branches apiece, arranged uni- 

 laterally. Caudal setae about | as long as the body, beset at the joinings with fine rigid 

 hair arranged piunately. The hairs of Ccen'is are not flattened like those described under 

 Tricorythus. Hind leg the longest ; the tarsus (claw excluded) about as long as the 

 tibia. Femora slender, or broad, according to the species. Antennae of moderate length ; 

 joint 2 rather long and pubescent ; the remainder of the flagellum beset at the joinings 

 with minute spreading hairs. 



Type. C. Imlterata (in Ephemera), Fab. 



Didrihution. Northern Europe and America, southwards to Egypt (Savigny), Mogador 

 (undescribed sp.), and Florida; lakes of East Ceuti-al Africa; Cape Town (undescribed 

 sp.) ; and the Indo-Malay region. 



Etymology . A mythological proper name. 



The adult flies take wing during the cool of the day, and during the warmer hours of 

 the night, when light is attractiA^e to them. Their life is fugitive in dry air. The Cape 

 Town and Mogador species were found there by me in 1874. and 1881 respectively ; but 

 in each case only a single drowned adult 2 was obtained. I have seen nymphs of C. dimi- 

 diata, halterata, Harrisella, and of some Portuguese and Italian species alive. My dis- 

 covery of the nymph occurred at Cambridge in the spring of 1866 ; but the genus and 

 species ( C. dimidiata) of the specimen captured were not ascertained until a year or two 

 later. 



C^Nis DIMIDIATA, Steph. Plate XV. 26. 



lEphemera minhnu, Liun., Syst. Nat. ed. v. p. 62 (1747) ; Mill., Zool. Dau. Prodr. 142 (1776) ; Schr., 

 Fn. Baica, ii. pars ii. 198 (1798).— [Sy/emera] or E. horaria, Linn., [Act. Upsal. (173G),p. 27; id., Fn. 

 Suec. ed. i. no. 754 (17-16)] ; id., Syst. Nat. ed. x. i. 547 (1758) ; id., Fn. Suec. ed. ii. 376; [Geof., 

 Hist. Abreg. d. Ins. Paris, ii. 240, no. 8 (1761);] Pontop., Naturh. Dan. 223 (1765); Linn., Syst. Nat. 

 ed. xii. pars ii. 907 (1767) ; Fab., Syst. Ent. 304 (1775) ; Mill., Zool. Dan. Prodr. 143 (1776) ; Fab., 

 Sp. Ins. i. 358 (1782) ; Fourc., Ent. Paris, ii. 352 (1785) ; Fab., Mant. Ins. i. 214 (1787) ; Berkcnh., 

 Outl. Nat. Hist. Gt. Brit. & Ireland, ed. ii. i. 150 (1789) ; Vill., C. Linn. Ent. iii. 20 (1789) ; Gmel., 

 Linn. Syst. Nat. ed. xiii. i. pars v. 2630 (1790) ; Ros., Fn. Etrusc. ii. 9 (1790) ; 01., Eneycl. Meth. vi. 

 419 (1791) ; Fisch., Vers. e. Naturgcseh. v. Livland, 566 (1791) ; Fab., Ent. Syst. emend, iii. pars i. 71 

 (1793) ; Schr., Fn. Boica, ii. pars ii. 199 (1798) ; Ccderb., Fn. Ingrica; Prodr. 135 (1798) ; Walck., Fn. 

 Paris, ii. 10 (1802) ; Lat., Hist. Nat. ed. ii. 226 (1817).— £. j^tumosa, Miil., Zool. Dan. Prodr. 142 

 (1776). — E. \\albipennis, Atkinson, Zoologist, i. 272-5 (1843). — E. lactea, Landois, Jahresb. Westf. 

 Prov. Ver. f. "Wissensch. u. Kunst. (1878), 3. 



? Brachycerais minima, Curt., Lond. & Edinb. Phil. Mag. ser. 3 (1834), 122. 



C<enis dimidiata, ! Steph., 111. Brit. Ent. vi. 61 (1835) ; Pict., Hist. Nat. Nevropt. ii. Ephem. 286 



