180 EEV. A. E. EATON ON EECENT EPHEMERID^ OR MAYFLIES. 



Adult. — Hind wings absent. Wings, of some species only, in the $ ov in both sexes, 

 varied with colour in the marginal and submarginal areas, and provided with cross 

 veinlets between the great cross vein and the bulla ; but other species have the wings of 

 the 6 or of both sexes devoid both of colour and of cross veinlets in the parts specified ; 

 intercalar rudimentary veinlets of the terminal margin single in a large majority of the 

 species ; cross veinlets of the disk disposed, as in Ba'etis, mainly in 3 dislocated sei'ies in 

 front of the cubitus (5) and 2-3 behind, many of them thickened slightly in the females 

 of some of the species. Forceps-limbs of 6 4-jointed ; the basal joint short, relatively 

 very stout, gibbous at the base and suddenly contracted near the distal joining on the 

 inner side ; the second joint less stout and larger at its base than at its further extremity; 

 the third joint comparatively long and slender ; swollen a little at the end ; the fourth 

 joint minute, clavate or papilliform. Penis not yet observed. Intermediate abdominal 

 segments of ? subequal in length. Caudal setse in im. s about 2, in $ l-lj '^^ loiig 

 as the body, in subim. s about f , ? about f as long as it. Fore tarsus of s nearly 1^ 

 as long as the tibia, which is almost of the same length as the femur ; its joints in order 

 of lessening length rank 2, 3, 4, 5, 1 ; fore tarsus of ? (exclusive of joint 1) little more 

 than f as long as the tibia, which is about \-^ as long as the femur ; its joints rank 2, 3 

 subequal to 5, 4, — 1 being extremely short and intimately combined with the tibia. Hind 

 tarsus of 6 about f as long as the tibia ; its joints, shorter than in the $ , rank 1, 1, 3, 2. 

 iSlymph. — Abdominal tracheal branchiae all foliaceous and slightly oblique, and all double 

 excepting the hindermost ; each of the double ones is formed of two unequal divisions 

 slightly connate at the base, containing somewhat palmately partite tracheae with long 

 branches and short branclilets ; of these divisions the larger, broadly subrotundate, is 

 more or less subtruncate along the costal border and displays a small contracted sinus at 

 its posterior base ; the smaller division exhilnts a similar sinus thereabou.ts, and a wide 

 shallow sinus or excision on the opposite side near the tip ; the single one of each series 

 is subrotundate, with a shallow recess in place of the basal sinus, and with the opposite 

 margin towards the tip slightly refuse, and is supplied by a single trachea divided nearly 

 to the roots into two main branches with unilateral branchlets. Antennae longer than the 

 head and thorax combined [in C. rufulum of equal length with the body]. Setae subequal 

 to each other and to the body in length, fringed for at least halfway to the tips from 

 the roots, with the ends of the fringes gradually shortened to points, and then tail-pointed, 

 the proportionate length of the fringeless tail-points varying with the species. Mandibles 

 terminated by compressed denticulate teeth ; endopodite absent. Palpus of maxilla i. 

 longer than the lacinia, 3-jointed ; first joint as long as the second, and almost twice as 

 long as the third ; the lacinia armed with slender fang-like teeth at the tip, preceded by 

 two evenly arranged divergent series of setulae along the inner edge. Laciniae of maxillae 

 II. falcate, narrower than the acutely lanceolate lobes of the labium ; proximal joint of the 

 palpus a little shorter than the remainder, which are dilated distally and slightly 

 compressed ; the terminal joint obliquely truncate at the end and acute at the extremity. 

 Median lobe of the tongue obtusely rounded, broader than the paraglossaj. Hind tarsus, 

 claw excluded, a little shorter than the tibia, and tliis scarcely more than ^ as long as the 

 femur ; the whole leg about \\ as long as the fore leg. Resident in still or sluggish 



