EEV. A. E. EATON ON EECENT EPHEMEEID^ OE MAYFLIES. 223 



some lights the costa, subcosta, aud radius, which are pitch-brown or light i^itch- 

 brown. 



S . Very similar. The ventral markings consist of a broad dark longitudinal stripe on 

 each side at a little distance from the pleurae in segments 2-5 or -6. The joinings of the 

 setae are more distinctly piceous than in the <^ , and this colom- seems to be liable to run 

 together into irregular bands, perhaps only in dead specimens. The terminal joints and 

 the joinings of the other tarsal joints are warm sepia-brown. Length of body, d 9, 2 10; 

 wing, d 10, ? 11 ; setae, c? im. 18-25, subim. 11, ? im. 15 mm. 



Hub. Denham, Mass. (IVfLach. Mus.) ; Worcester, Mass. (Mus. Comp. Zool. Cambridge, 

 Mass.). 



No Japanese Siphlums has yet been described; but in M'Lach. Mus. are 9 adult 2 

 specimens (captured by Pryer) of a large species. The colours of the abdomen have been 

 lost, and therefore it is inexpedient to describe the insect. 



ONISCIGASTER, M-'Lach. 1873. 

 Illustrations. Adult (details), PI. XXI. 36 ; (Avhole figures) see citations under 

 0. WahefieUU of M^Lach. (1873 & 1874). Nijmph PI. LI. ; see also citations of M-'Lach- 

 (1874) and Vayssiere (1882). 



Adult. — Fore leg of S shorter than the body nearly in the proportion of 14 to 17 ; 

 tarsus almost 1^ as long as the tibia, and this nearly ^ as long as the femur ; gradation 

 of the tarsal joints in the order of lessening length, 1, 2, 3, 4, 5, the first about 1^ as long 

 as the second joint. Fore leg of ? little less than half [^] as long as the body ; tarsus 

 about If as long as the tibia, and this f as long as the femur ; the rank of the tarsal 

 joints in order of diminution is 1, 2 equal to 5, 3, 4, and the first is twice as long as the 

 second joint. Hind tarsus of $ about 1^ as long as the tibia, and this little more than 

 \ as long as the femur ; the joints in order of shortening rank 1, 5, 2, 3, 4, and the first 

 is twice as long as the second. Ungues each unlike the other in every tarsus. Hind 

 wing well developed, obtusely subovate ; dilatation of the marginal area obtuse in 

 front ; axillar region well developed, largely occupied by numerous long anastomosing 

 veinlets from the inner margin. In the ? abdomen the relative lengths of segments 

 2-10 may be formulated thus :— 6, 8, 8, 8, 8, 10, 11, 10, 6 ; the first is thoracoid. Pleurae 

 of segments 2-5 in $ squarely truncate behind; those of segments 6-9 in 2, or 5-9 

 in c? , broadly and oniscoidally dilated, each narrowed and rounded oflf obtusely in front, 

 ind each produced behind into a short acute point separated by a smaU sinus from the 

 und border of the segment, so that this part of the abdomen is flanked by very con- 

 spicuous serratures ; the pleural projections of segment 5 in the i are narrower than 

 he others. The 9th ventral segment is unprovided with a lobe in the ? . Forceps-basis 

 )ipartite ; the divisions, explanate, quadrangular, longer than broad, and remote from 

 )ne another, might be reckoned as basal joints of the forceps-limbs. Forceps-limbs 

 lactyloid, 4-jointcd ; the first joint short, tapering from the base ; the second curved, 

 onger than the others, and very slightly gil)bous inside at the base. Penis smaU, 

 erhaps retracted partially in dried examples. Median caudal setaj of <S about \, of ? 

 as long as the body ; outer set?B of i about | as long as the body. In the 2 



