REV. A. E. EATON ON RECENT EPHEMEEIDiE OR MAYFLIES. 137 



texture of the wings and approximation of the anal (8) to the pobrachial (7) nervure at 

 the base of the mesothoracic wing, and the brevity of the subimago period. The pro- 

 notum of the adult, similar in some respects to that of Epliemerella, has also an appreci- 

 able likeness to that of Lachlania and its allies; and it is noteworthy that free epinotal 

 prolongations of the membrane continued from the wing-roots along the hind margin of 

 the mesonotum, similar to theirs, exist in Leptohyplies — Lachlania and its kindred ranking 

 next to the section of Polymitarcys, in the present system of arrangement. In marshal- 

 ling European collections I have sometimes placed Ca;nis between Oligoneuria and Foli/- 

 mitarcys ; and I believe Dr. Hagen and Mr. M'Lachlan are disposed to assign it that 

 position. 



But, on the other hand, at the present time no genus unquestionably referred to 

 Group I. is known to have palpi conformable to the Leptophlehia type. Even Jolia, so 

 similar in aspect to nymphs of the Baetis and Siphlvriis sections, has palpi of the Palin- 

 gen'ia type ; and Enthyplocki, while deviating slightly from the normal, clearly maintains 

 through Ephemera a close connexion with the same group. If the transfer has to be 

 effected eventually, on account of anything learned about nymphs yet to be discovered 

 of genera in Group I., the consequent disturbance in the grouping of the sections may 

 attain very considerable dimensions. 



Section 7 of the Genera. — Type of Ctenis. Adult. — Pronotum of $ transverse and 

 short, closely appressed to tlie mesonotum, prominent and somewhat smooth above, and 

 witli a deep sinus in the middle of its hinder border. Hind tibia about f as long as the 

 femur, the tarsus little more than h as long as the tibia. In the mesothoracic wing the 

 longitudinal neuration is fully developed ; the first and second axillary nervures (9^ & 9") 

 enclose a narrow space, whicli for some distance from the inner margin maintains an 

 almost even width, and docs not extend to the wing-roots ; wing-membrane ciliated 

 along the inner and terminal margin, as in the subimago [except, perhaps, in Lepto- 

 hyphes]. Hinder ocelli unusually large ; the foremost extremely small [excepting^ 

 perhaps, in Tricorythiis maximus]. Nymph \Leptohyphes unknown]. — Terminal margins 

 of the wings free [excepting, probably, in Leptohyphes]. Palpus of the 1st maxilla 3- 

 jointed, longer than the lacinia ; the latter crowned with a sparse tuft of hair, armed 

 with spinous teeth at the tip, and ciliate on the inner edge. Lobes of the labium well 

 developed, subovate, nearly as large as the lacinige of the 2nd maxilte, which are ovate 

 and acute. Abdominal tracheal branchiae on segments 1-6; those of the first segment 

 minute and erect ; those of the 2nd segment elytroid, shielding the remainder, and 

 differing from all the others in form and texture. Hinder lateral angles of the segments 

 more or less prolonged. Natation laboured, aided by movements of the legs. 



Nymphs of two genera in this section are known— Cmiis and ? Tricorythus. Ccenis 

 has plumose caudal seta?, sparingly branched fringes to the hinder tracheal branchiae, 

 and has no appendages beneath their laminne. The other nymph has the setse minutely 

 pubescent and setulose, like those of Ephemerella, laxly pectinate fringes to the obtected 

 tracheal branchia?, and an appendage on the underside of each lamina of the hinder 

 pairs. 



