1873.] J- 15 [Horn. 



Male. Fifth ventral broadly emarginate, sixth concave deeply emargin- 

 ate, the eniargination at bottom rounded. 



Female. Fifth ventral truncate, sixth broadly rounded at tip. 



Hind tibial spurs slender acute, the inner longer. 



Occurs abundantly on the plains east of the Rocky Mountains from 

 Nebraska to New Mexico. 



0. eompressicornis, Horn, Trans. Am. Ent. 1870, p. 91. 



Color blue, sometimes inclining to violet, surface moderately shining. 

 Head shining, very sparsely punctate. Thorax nearly spherical, narrower 

 than the head, sides moderately arcuate, sparsely punctate. Scutellum 

 feebly channeled sub-truncate at tip. Elytra twice as wide at base as 

 thorax, gradually wider toward apex, surface punctate scabrous, less 

 shining than the head and thorax. Body beneath darker than above, 

 legs nearly black. Length .30-.50 inch ; 8-12 mm. 



Male. Antenna? much flattened, joints 5-10 twice as wide as long. 

 Fifth ventral feebly emarginate, sixth trapezoidal, concave, acutely 

 emarginate. 



Female. Antenna? with joints 5-10 broader than long. Fifth ventral 

 truncate, sixth oval at tip. 



Spurs of hind tibia? as in the preceding species. 



Occurs in Owen's Valley, California. 



C. convexa, Lee. Proc. Acad. 1853, p. 336. 



Head black, moderately shining, sparsely punctate. Thorax black, 

 moderately shining, very sparsely punctate, narrower than the head, 

 sides in front broadly rounded, behind slightly convergent, disc convex. 

 Scutellum rounded at tip, middle not sulcate. Elytra at base twice as 

 broad as thorax, gradually dilated toward apex, surface punctato-scabrous, 

 with faint bluish lustre. Body beneath shining, black, with faint bluish 

 tinge. Legs black. Length .48 inch ; 12 mm. 



Male. Antenna? moderately compressed, joints 5-10 not wider than 

 long. Anterior tibia? without terminal spurs. Anterior femur near base 

 with a short spur. Fifth ventral truncate, sixth semi-circularly emar- 

 ginate. 



Female. Unknown. 



Hind tibial spurs as in the preceding species. 



Occurs in Texas. The curious male characters at once distinguish it. 



In the preceding description much detail has been avoided as not perti- 

 nent to the object of the essay, and characters common to all the species 

 have for the most part been entirely omitted except in the synoptic 

 tables. The rufous spot of the vertex has scarcely been noticed, as its 

 presence or absence has merely individual value. Only such points have 

 been touched upon as will enable the student to recognize with ease any 

 species in the collections and determine thereby those which are unknown. 



Pomphopoea. Lee. 

 This genus differs but slightly from Cantharis (Lytta), the only point 

 of difference being in its deeply emarginate labrum. The species have 



