230 EEV. A. E. EATON ON RECENT EPHEMERID.E OR MAYFLIES. 



natiug in several (about 5) curved subulate teeth ; palpus minute, setaceous, 11-joiufced, 

 with the second joint the longest, and the third, nearly equalled in length by the penul- 

 timate, longer than any of the remaining joints. Laciniaj of maxillaj ii. broadly falcate, 

 almost as broad as the subquadrangular lobes of the labium ; palpus 13-li-jointed ; the 

 first joint much tlie stoutest and longest, about half as long as the flagellum; the second 

 joint (the first of tlie flagellum) longer than any of the others. Terminal margins of the 

 fore wings free. Hind leg little longer than the fore leg ; tarsus about ^ as long as the 

 tibia, and this about § as long as the femur ; all the legs are fringed with hair along 

 their upper edges, and have strongly incurved ungues. Seta3 defective ; the median 

 plumose, the others ciliated within. Length of body 21 mm. 

 Hab. Chili (Reed, in M°Lach. Mus.). 



Tart lY. Read December 17th, 1885. 



Third Series of Group III. of the Genera of the Ephemeridce. 



AdulL — Anal-axillar interspace of tlie fore wing curvilinear-trilateral, subtended by 

 the anal angle and a part of the terminal margin. Porccps-basis of d well developed — its 

 form and that of the penis (especially the latter) facilitate distinctions of genera ; forceps- 

 limbs either 4 -jointed, with the second joint proportionally very long, or 3-jointed (through 

 coalescence of the first with the second joint), with an enlargement at tlie base of the 

 proximal joint. Njmph [those of section 13 unknown] : palpi of maxillai i. and ii. 

 2-jointed and geniculated ; terminal joint of the palpus of maxilla ii. peculiarly 

 pouched. Abdominal tracheal branchiiie [excepting the hindermost in some genera] 

 foliaceous and fringeless, furnished at the base each with a fascicle of fibrils or an annexed 

 lamella filiformly dissected at the edges. 



Section 13 of the Genera. — Type of Atopopus. Adult. — In the fore wing the first 

 axillary-nervure (9^) meets the inner margin at or near the very obtusely rounded anal 

 angle ; the second axillary (9-), subparallel with and adjacent to the first, receives several 

 branchlets [or curved cross veinlets] from the distal portion of the inner margin which 

 comes between its own termination and that of the third axillary nervure (9-'); the 

 almost straight anal nervure (8) meets the terminal margin rather far in advance of 

 the anal angle ; the trilateral, somewhat leg-of-mutton-shaped space [the " anal-axillar 

 interspace"], bounded by the anal and first axillary nervures together with the terminal 

 margin, and attenuated towards the wing-roots, contains a variable numlier of inter- 

 calary nervures, incursive from the terminal margin and commonly grouped together 

 in two couples of unequal length, of which the longer [usually the nearest to the first 

 axillar (9^)] extends about halfway to the wing-roots. Tarsi of the hinder legs as long 

 as the tibiic or longer. Nymph unknown ; perhaps that ranked in section 12. 



Absence of requisite materials precludes description of the genera of this section in 

 full detail. 



