COLEOPTERA. 143 



convex ; punctures rather large, very closely crowded, evenly distributed : 

 interspaces coarsely graiiulose ; ocular lines meeting at scarcely one-half a 

 length in advance ; antennae slightly longer than the width of head, rather 

 robust, piceous-black, club rather prominent; third joint scarcely one-fifth 

 longer than the fourth, fourth and fifth equal, sixth and seventh equal in 

 length, and sub-equal in thickness, eighth thicker than the seventh, slightly 

 elongated, last two joints much thicker than the ninth ; maxillary palpi 

 rather slender, first joint fulvous, second piceous-black, paler at base, third 

 short, rather slender, piceous-black. Prothorax widest at one-third the 

 length posteriorly, where it is five-sixths as wide as the head, and narrower 

 than long ; sides thence moderately convergent posteriorly, long, feebly 

 sinuate; anterior margin much longer than the posterior, equally arcuate; 

 surface feebly tuberculate near the basal angles', impressed on the flanks at 

 one-third the length from the apex ; having a deep, rounded, prominent 

 impression near each anterior angle ; finely, very closely, somewhat evenly 

 punctate ; interspaces narrow, uneven, distinctly granulose ; canaliculation 

 terminating at a distance from the base and apex equal to one-fourth the 

 length, roundly impressed, deep, fusiform, and conspicuous, bottom impunc- 

 tate. Elytra at base wider than the head; sides very feebly divergent poste- 

 riorly, slightly longer than the width at base, strongly arcuate, more strongly 

 so posteriorly ; together broadly, roundly, and very strongly emarginate be- 

 hind; suture one-fourth longer than the pronotum ; surface deeply impressed 

 on the suture at the base, feebly impressed near the humeri ; rather coarsely, 

 very closely, most irregularly, and tortuously channeled. Abdominal seg- 

 ments decreasing uniformly ami rather rapidly in width, first slightly nar- 

 rower than the contiguous elytra ; border nearly obsolete except on the first 

 segment ; surface very coarsely, closely, variolately, and evenly punctulate ; 

 interspaces coarsely granulose; transverse carinae tricuspid, cusps nearly 

 equal in length, rather finely acuminate, long, and prominent. Legs very 

 slender, dark piceo-fus'cous ; first joint of the posterior tarsi one-half longer 

 than the second and distinctly shorter than the last, second, third, and 

 fourth uniformly and rapidly decreasing in length ; all the joints are coarsely 

 granulose. 



Mule. — Unknown. 



Female. — Sixth 'ventral segment very obtusely rounded behind. 



Length 3<0 mm. 



Colorado, 2. 



This species may be distinguished at once from vacuus by the 

 under surface of the abdomen, which in the latter is highly polished, 

 very sparingly pubescent, minutely and sparsely punctulate, while in 

 the former it is coarsely and closely punctulate, and the interspaces 

 are minutely, though distinctly, granulose or reticulated. The struc- 

 ture of the prothorax of amicus is peculiar and very unusual in the 

 genus, and renders the species very distinct. 



123. S. exilis n. sp. — Form slender. Pubescence short, stout, extremely 

 sparse, semi-erect, plumbeus, somewhat fulvous on the head. Head mode- 



