EPHEMERELLA.—TRICORYTHUS. 11 
noted as ‘‘ emarginate or shortly excised ;” posterior lateral angles of the dorsum of the 
same segment acutely produced. Sete (now lost) 3, subequal. ‘Tarsi as in Adeno- 
phlebia; intermediate leg of ordinary proportions. | 
The specimen in dying began to shed its slough. The following particulars are note- 
worthy concerning it:—-Wings sepia-brown, with pitch-black neuration variable in 
detail; in the marginal area of the fore wing are about seven cross-veinlets before and 
thirteen beyond the bulla; those in the disk are rather irregular in their arrangement. 
Sete very light sepia-grey, with black joinings. Body piceous. Fore femora piceous; 
tibie and tarsi lighter. Hinder femora seemingly with a narrow pale band nearly 
in the middle. 
Length of wing 9 millim. 
EPHEMERELLA. 
Ephemerella, Walsh, Proc. Acad. Phil. 1862, p. 877; Eaton, Rev. Mon. Ephem. p. 124, t. 14. 
figg. 24.a-c (adult details) and t. 87 (nymph) (1884). 
This genus inhabits Northern Temperate regions, ranging to the Kullu Himalaya. 
Probably largely represented in America, whence six species and several allied nymphs 
have been described, and others are extant in collections (cf. Eaton, op. cit. p. 131). 
A 2 subimago in Messrs. Godman and Salvin’s collection, labelled N. Sonora, 
Mexico (Morrison), gives indication of the southerly range of this genus in America. 
TRICORYTHUS. 
Tricorythus, Eaton, Ent. Monthly Mag. v. p. 82 (1868) ; Rev. Mon. Ephem. p. 188, t. 15. fig. 25 
(1884) (adult details) (nymph, t. 41, doubtfully referred here). 
A small African, Malayan, and Subtropical American genus, of doubtful occurrence in 
the south of Europe. 
1. Tricorythus explicatus, sp. n. (Tab. I. figg. 8, 8 a.) 
Adult (dried).— 3. Body pitch-black, slightly browner in some (doubtless just moulted) specimens, "Wings 
vitreous; neuration indistinct to the naked eye, except when held up to the light ; subcosta and radius, 
except near the base of the wing, greyish-black. Femora pitch-brown, as are also the anterior tibie in 
some lights; hinder tarsi and tibie towards their lower extremities impure yellowish-white or pale 
amber. Setze (flattened in drying) vitreous, with black edges and joinings. 
Q. Very similar to the 3, but with the body pitch-brown. 
Length of body, ¢ 4, 9 3; wing, ¢ 5, 97; seta, ¢ about 10, 2 3:5 millim. 
Hab. Mexico, N. Sonora (Morrison; forty-one ¢, four ¢ ). 
The wing of this species differs from that figured by me in the year 1884, cited 
above, in the following particulars :—Marginal area devoid of cross-veinlets; the ante- 
rior intercalary nervure of the anal-axillar interspace meets the first axillar nervure 
c2 
