on the Hphemeride. 95 
Cenis dimidiata. 
(Genitalia maris, Pl. V. fig. 5. Ala antica, Pl. IT. fig. 4.) 
Ephemera minima, (?) Lin. 1747. E. horaria, (?) Lin. 
1758. Brachycercus minima, (?) Curt. 1834. Ccenis dimi- 
diata, brevicauda & pennata, Ste. 1835-6. Cloe horaria, 
(?) Ramb. 1842. 2H. albipennis, Atk. 1843. Cloeon horaria, 
(?) Walk. 1853. 
Subimago, v. v.s. Alz cane, areis et marginali et 
submarginali fuliginosis pene usque ad apices. Setz 
albze, pubescentes. 
Imago, v. v. s. Caput et prothorax fusci, obscuri, 
antennis albis, oculis atris. Meso- et meta-thoraces picei. 
Pedum antici sub-fuliginosi, femoribus griseis ; posteri- 
ores cani, puncto atro ante femoris apicem. Abdomen 
vel in toto album vel cretaceum ; szpissime tribus seg- 
mentorum apicalium tantum cretaceis, et ceteris griseis, 
juncturis lineaque longitudinali media cretaceis. Ventris 
segmenta sexpe griseo bi-punctata sunt. Genitalia et 
setze albee. 
Long. corp. go 3-5, ? 4; al. ¢ 4, 2? 3; set. dGI8SS& 
13, subim. 3 & 2°5-3 & 3°53; sat. 9 38, subim. 2°25 mm. 
Hab.—England; Visp in the Valais; Belgium (De 
Selys Mus.); Prussia (Hag.); Moscow (Oul.). From 
June to August. 
Cenis diminuta. 
C. diminuta, Walk. 1853. CO. amica, (?) Hag. 1861. 
(Genitalia maris eis preecedentis parum similia.) 
Imago, v. s.s. Thorax luteus: alis vitreis, costas ver- 
sus nigricantibus; pedibus albis, femoribus anticis cin- 
erascentibus. Segmentorum abdominis anteriora sub- 
virescenti-grisea, posteriora cretacea ; segmentis singulis 
ad latera lineis obscuris longitudimalibus. Genitalia et 
setz albe. 
Long. corp. g 2°5, al. 3, set. 10°5 mm. 
Hab.—S. John’s Bluff, East Florida (E. Doubleday) ; 
Pennsylvania (Hag.). 
The posterior femora of C. amica, Hag., have each a 
superior subapical black spot; but I suspect it will be 
found to be identical with C. diminuta, Walk. 
