328 GEO. H. HORN, M. D. 



whitish pubescence. Anterior and middle legs rufous, hind legs black, tarsi 

 black. Length .12— .14 inch ; 3—3.5 mm. 



This species is very distinct from any in the group. The vestiture 

 gives it an unmistakable appearance. 



This species is found on the Iron wood tree of Arizona. 



Group VI. 

 This group contains a small number of small species differing from 

 the preceding group in the possession of a small denticle in addition 

 to the main tooth. The tooth is small and the emargination of the 

 femur within which it is situated, is slight, the denticle scarcely evi- 

 dent or even obsolete. The group can hardly be considered of equal 

 value to those which precede, although the species cannot be strictly 

 referred to those which follow. The ninth group is also of doubtful 

 value as the minute denticulation does not appear to be equal among 

 the individuals of the species and any decided enlargement of a denti- 

 cle would refer the species to some other group. Among our species 

 we always find the primary tooth quite distinct. The denticle that is 

 sometimes present and occasionally obsolete might seem to be too 

 slight a character for the separation of these species from the preced- 

 ing group. In the group which precedes the tooth is always of moder- 

 ate size, acute and with the emargination of the femur very decidedly 

 marked. Our species are three, all small, elongate oval, of rather 

 slender form, more attenuate in front and with the pygidium decidedly 

 oblique and never vertical as is seen in most of the species of all the 

 preceding groups. They may be distinguished in the following 

 manner : 



Color testaceous; clothed with pale yellowish-white pubescence. 



desertorum. 



Color black, more or less concealed by pubescence. 



Yellowish pubescence densely placed, concealing surface color. ..aureolus. 

 Cinereous or whitish pubescence sparsely placed, surface color evident. 



pauperculus. 



B. desertorum, Lee, Proc. Acad., 1858, p. 7S. — Oblong oval, pale testa- 

 ceous, clothed with whitish pubescence. Head testaceous, front and occiput 

 dark brown, densely punctulate and clothed with whitish pubescence. Anten- 

 nae pale testaceous, scarcely extended to base of thorax, Thorax trapezoidal 

 not wider at base than long, sides nearly straight and gradually narrowed to 

 apex, base feebly lobed at middle, lobe truncate, on each side straight; surface 

 convex, coarsely punctured and rugulose, dotted with whitish pubescence; 

 color variable from pale testaceous to piceo-testaceous. Scutejlum twice as 

 long as wide, clothed with white pubescence. Elytra above flat or very feebly 

 convex, not wider at base than thorax, then gradually wider to a point in front 



