EEV. A. E. EATON ON EECENT EPHEMEEID^ OE JMAYFLIES. 107 



other ; fore tarsus of d subequal in length to the tibia, which is nearly twice as long as 

 the feniLir; the joints in diminishing sequence rank 2, 3, 4, 5, and 1. Hind tarsus 

 (including joint 1) nearly ^ as long as the tibia; its joints rank 5, 2 subequal to 3, 



1 and 4; the proximal joint is ill defined in dried examples. Nymph latent ; abdominal 

 tracheal branchise all bipartite ; those of segment 1 with simple tiliform divisions beset 

 with short minute hairs ; those of the other segments decumbent upon the sides of the 

 dorsum, with simple oblong-ovate foliaceous divisions, fimbriate simply at the margins. 

 Caudal sette about as long as the body, similar to those of LeptopJdebia. Mandibles, 

 labium and second maxillae, tongue and paraglossae, very similar to those of Choroterpes ; 

 but the last are abrupt and emarginate, instead of acute, at the tips. MaxiUa i. also 

 subsimilar to that of Choroterpes ; but there is no spine below the subterminal series of 

 pectinate setulre on the lacinia, the palpus proportionally is rather shorter, and joints 



2 and 3 together are subequal to 1 in length. Abdomen slender, slightly dilated at 

 the sides ; the hinder latei'al angles of segments 8 and 9 shortly prolonged and acute. 

 Hind leg rather the longest ; the tarsus (claw excluded) about \ as long as the tibia. 



Type. Th. bellus, Etn. 



Distribution. Portugal ; Central America (an undescribed sp.) ; also (provisionally 

 referred species) Columbia and Lahat. 



Etymology, OpavXoc, fragile. 



The nymph of the typical species was identified, chiefly by inference from the local 

 fauna of the stream where it was found, and partly by the structure of the genitalia 

 of advanced specimens. The neuration of the fore wings of certain Central- and South- 

 American species provisionally referred here {Th. mexicimas &c.) departs slightly from 

 the type in the following particulars :— Cross veinlets are plentiful in proximity to the 

 terminal margin, and the longitudinal nervures terminating in that margin are more 

 frequently branched than in normal species. The intercalar uerviu-es of the anal axillar 

 interspace towards their anterior extremities curve forwards to uoite each with the 

 nervure next in advance, in the manner usual in species of Atalophlebia. Some of these 

 species have cross veinlets before the bulla in the marginal area. 



Thraulus belltjs, Etn. Plate XII. 20 (wings, legs, forceps, and penis). Nymph, 

 Plate XXXV. 



Thraulus bellus, ! Etn., Ent. Mo. Mag. xvii. 195 (1881). 



Subimago. — Wings light blackish grey. 



Imago {living), <3 .—Eyes intense warm sepia-brown. Body blackish piceous ; thorax 

 jet-black above, with pale sutures. Legs piceous ; the fore tarsi blackish, the hinder 

 tibice and tarsi lighter. Wings vitreous, with light pitch-brown neuration ; the margmal 

 area of the fore wing contains about 12 weU-defined and 3-4 very indistinct straight 

 cross veinlets in the pterostigmatic region, but none before the bulla. Length of body, 



d 8, ? 7 mm. 



Hab. Portugal, in the stream below Cintra. The nymph was discovered at the end of 

 April 1880.. To find the imago, I revisited the locality on the 1st of June, early in the 



