171 EEV. A. E. EATON ON EECENT EPITEMETIIDtE OE MAYFLIES. 



that meet the apical margin at an acute angle. Hind tarsus, claw excluded, very nearly 

 of the same length as the tibia ; the leg, as a whole, rather longer than the fore leg. 

 Length of body 8, setfE 4 mm. 



Bah. Puno, Peru ; from a spring (A. Agassiz, Mus. Comp. Zool. Cambridge, Mass.). 



CENTROPTILUM, Etn., 1869. 



Illustrations. Adult (details), PI. XVII. 30, a-c, and LXIV. 21 ; (whole figure) see 

 citations of Pictet (1843-5) under C. lideolnm {Cloe translucida), and C. lituratum. 

 Nymph., PL XLVI. 



Adult. — Hind wing oblique, elongate, and narrow, with the apex commonly obtuse, 

 rarely acute, and usually with the costal projection acuminate [acute in C. stenopteryx] ; 

 neuration limited to 2 simple longitudinal nervures. Pore wing devoid of colour- 

 ornamentation, free from cross veinlets in the marginal and submarginal areas as far 

 from the great cross vein as the bulla?, and with the iutercalar veinlets of the terminal 

 margin in a large majority of the species single [paired in C. Poeyi'] ; neuration, as a 

 Avhole, similar to that of species of Cloeon or Ba'etis. Porceps-limbs of d mostly after 

 the j)attern of Cloeon, which differs froin that of tlie normal Ba'etis in the greater relative 

 plumpness of joint 2, in the slight terminal enlargement of joint 3, and in joint 4 being 

 clavate or papilliform instead of oval ; C. tenellum (PI. XVII. 30 c) is tlie only known 

 deviation fi'om this type of forceps in the genus. The interval between the bases of the 

 force])s-limbs varies in relative width with the species. Intermediate abdominal segments 

 of $ subcqual in length. Caudal setas in 6 im. If- 2, in ? im. about 1^, in subim. 1-1^ 

 as long as tlie body. Pore tarsus of 6 rather longer tlian the tibia, which is about twice 

 as long as the femur ; its joints in diminishing sequence rank 2, 3, 4, 5, 1 ; fore tarsus of 

 ? nearly -^q as long as the tibia, which is almost as long as the femur ; its joints in 

 shortening succession rank 2, 3, subequal to 5, 4, 1. Hind tarsus of 6 about | as long 

 as the tibia ; the joints (longer in the ? ) rank 1, 4, 2, 3. Nymph. — Abdominal tracheal 

 branchite acute, the foremost narrowly obovatc-lanceolatc, tlie others more broadly ovate, 

 each traversed lengthwise by an irregularly pinnately branched trachea. Antennge 

 longer than the head and thorax combined. Outer caudal setse almost ^ as long as the 

 body, the median about f as long as it, all shortly tail-pointed in the typical species. Man- 

 dibles armed with slender fang-like teeth ; endopodite absent, or represented by a minute 

 tuft of hair. Palpus of maxilla i. slightly longer than thelacinia, 3-jointed, with slender 

 joints of nearly equal length ; the lacinia terminated by fang-like teeth, preceded on the 

 inner edge by an even series of setulae inserted at nearly equal intervals. Lacinise of 

 maxillae ii. falcate, scarcely wider than the somewhat subulate lobes of the labium; 

 proximal joint of the palpus rather shorter than the remainder, which are compressed; 

 terminal joint squarely truncate, oblong, quadrangular, and barely more than | as long 

 as the second. Tongue similar in form to a closed ecclesiastical biretta ; the median lobe 

 broader than the paraglossae, and minutely mucronate. Hind tarsus, claw excluded, 

 subequal in length to the tibia ; the leg altogether about 1^ as long as the fore leg. 

 Habits, those of Baetis. 



