GEOLOGICAL SUEVEY OF THE TEREITOEIES. 447 



Female. — Frontal cone elongate, flat above, scarcely margined, a shal- 

 low foveola eacli side nuder the lateral margin. Face very oblique, 

 quadricarinate; carince sharp, divergent, reaching the clypeus. Eyes 

 oblong-ovate, situated near the antennae. Antennse ensiform, trique- 

 trous. Pronotum about as long as the head; anterior and posterior 

 margins truncate; cylindrical. Elytra narrow, lanceolate, reaching the 

 fifth abdominal segment; wings small. Abdomen elongate, cjdindrical, 

 slightly enlarged toward the apex ; upper valves of the ovipositor 

 scarcely exserted. Prosternal spine quite short and blunt. Mesosternum 

 slightly furrowed longitudinally on each side. 



Color. — Bright pea-green, immaculate ; wings pellucid. After immer- 

 sion in alcohol it becomes a pale greenish-yellow. 



Male. — Differs from the female, as follows : Much smaller and slen- 

 derer ; vertex more pointed, slightly margined ; abdomen turned up at 

 the apex, terminating with a sharp lanceolate extension of the last 

 ventral segment; antennae, face, vertex, occiput, pronotum, femora, and 

 abdominal appendages more or less varied with pale carneous ; a whitish 

 stripe extends from the lower border of each eye to the base of the 

 middle leg. 



Dimensions. — $ , length, 1.05 inches; elytra, .52 inch ; posterior femora, 

 .5 inch. (5^ , length, .78 inch. 



Found on the east side of the Black Hills, Wyoming, in the vicinity 

 of Cottonwood Creek. August. 



I formerly i)laced this in Mesops, with which it agrees in all respects, 

 except the position of the eyes, which api)ears to be the distinguishing 

 character of that genus. I have, therefore, concluded to place it in 

 Ojjomola, in Walkers second group, of which 0. cylindrodes, Sial., is the 

 type; yet I believe it would be better to slightly modify the generic 

 description of Mesops and place it there, for it appears to be very closely 

 allied to M. pedestris, Erichs. Certainly it agrees more closelj^ with the 

 characters of this genus (except as to the position of the eyes) than M. 

 gladiator, Westw. PI. II, Fig. 8. 



Second group. — Acridini. 



ACEIDIUM, Geof. 



A. amhiguiim, nov.'sp. 



2fale and female. — Very similar in size, markings, and carvings to 

 A. Americamim, Dm., w'ith which it has been long confounded, and 

 from which it differs chiefly, and almost exclusively, in the general 

 color. The A. Americanum is more deeply and closely punctured about 

 the head than the latter. In the former the frontal costa, besides the 

 smaller i)unctures, has along each margin a row of regularly spaced 

 large black punctures, which are less distinct, or wanting, in the latter, 

 (amhiguum.) The spots on the elytra of the latter are scarcely as large 

 and paler than in the former. 



Color. — Yellow or brownish-yellow. Face yellow; occiput pale brown. 

 Dorsum of the pronotum light brown ; the dorsal stripe dim, and some- 

 times, especially in the male, absent. Sides of the pronotum yellow ; a 

 dusky spot iii the middle witb a yellow stripe through it. Wings trans- 

 parent, with a pale-yellowish tinge at the base ; veins of the apex and of 

 the anterior ijortion black. Brownish spots on the elytra, m.uch like 

 and arranged as in A. Americanum; general color of the rest yellowish, 

 or brownish-yellow. Abdomen greenish-yellow. ..Legs bright yellow; 

 femora reddish above. 



