ii GEORGE H. HORN, M. D. 



piccous; abdo)nen, especially at the sides and tip, paler. In this 

 species, as iu americanum, the dark spaces of the elytra are but fiiintly 

 tinged with metallic green. Length .27 inch ; 7 mm. 



A single specimen collected at Camp Grant on the San Pedro 

 River, a tributary of the Gila, Arizona. 



0. dentatum, Lee. Ann. Lye. V, p. 200. 



Resembles fjilse in form and markings. The thorax is however 

 longer and with the pale margin and a discal transverse space scarcely 

 punctured, and the median line more feebly impressed. The metallic 

 discal transverse band is longer and approaches more nearly the mar- 

 gin. From the other species of the group it differs by having the 

 punctures of the strige at the apical third of the elytra almost entirely 

 obliterated. Length .28 inch ; 7 mm. 



Occurs on the banks of the Gila in Arizona, Fort Yuma, Teraecula, 

 Posey Flat, Owen's Valley, and other regions bordering the Colorado 

 Desert of California. 



0. americanum, Dej. Sp. 5, p. .583 ; Sayi Kirby, Fauna Bor. Am. IV, p. 65. 



This species is so widely distributed as to need no description. The 

 elytral interspaces are here more convex than in any other of our 

 species, the punctures of the stride rather fine and approximated and 

 distinctly visible almost to the apex. The median thoracic line is 

 faint. The disc of the thorax is dark brownish, slightly tinged with 

 metallic green. The lateral margins pale, narrow, suddenly dilated 

 at apical end, and with a narrow extension along the base, for a short 

 distance. Length .24 — 28 inch ; 6 — 7 mm. 



Occurs in Canada, New England, Middle and Western States. 



0. tesselatum,Say. Journ. AeacL III, p. 52 ; Lecontei Dej. Spec. V, p, 5S2. 

 Resembles r/Ux and dentatum by the elytral ornamentation. The 

 striae are very distinct at apex and the punctures closely placed in the 

 discal region are more distant near the apex, but still quite strongly 

 impressed. The dark rhomboidal spot formed by the dilatation of the 

 dark sutural line, seen in the two species above mentioned, is here 

 absent. The thorax coarsely but sparsely punctured, the discal space 

 and the lateral marginal region with but few punctures. The median 

 line is moderately impressed. The discal metallic spot is short equal- 

 ling about one-third the width of the thorax and with narrow processes 

 extending to the basal anxi apical margins along the median line. 

 Under surface ferruginous, margins and apex of abdomen paler. 

 Length .26 inch; 6.5 mm. 

 Canada and Middle States. 



