96 MEMOIRS ON THE COLEOPTERA 



it is difficult to say definitely with the relatively small material at 

 hand, as, in at least one case, the two terminal joints of the same 

 individual are different, and yet it is difficult to understand how 

 the profound concavity of the apex, sometimes reducing the lateral 

 outline of the joint to a slender arc, could have been brought about. 

 The prothorax is transverse, always bisinuate at base, with more 

 or less posteriorly prominent and acute basal angles, this thoracic 

 conformation being the chief character distinguishing it from Pele- 

 cyphorus. The elytra are always margined at the sides, the acute 

 margin terminating at some distance from the apex, and each has 

 two acutely formed subeven discal ridges, frequently united pos- 

 teriorly about opposite the end of the marginal ridge and with the 

 concave intervals transversely and unevenly folded or crumpled; 

 the humeral angles are obtuse and more or less rounded, but the 

 sides of the basal margin are laterally prominent and acute, because 

 of a constriction immediately posterior thereto. The prosternum 

 between the coxae is strongly deflexed posteriorly, with its surface 

 impressed along the median line. The legs are rather slender, 

 moderately long and comparatively weak, the tarsi somewhat 

 short but not stout, briefly spinulo-setose beneath, the anterior 

 tibiae moderately everted externally at tip and acutely pointed. 



The species are moderately numerous but very local, those re- 

 presented in my collection being separable as follows: 



Pronotum with very coarse, close and more or less confluent punctures. . 2 

 Pronotum with much smaller, widely separated though irregularly dis- 

 tributed punctures 1 1 



2 Sides of the prothorax not or but feebly serrulate 3 



Sides of the prothorax strongly and very distinctly serrulate 10 



3 Prothorax moderate or small in size, as a rule but little more than 



one-half as wide as the elytra in either sex 4 



Prothorax large, always much more than half as wide as the elytra. . . .5 

 4 Elytral pubescence extremely minute and inconspicuous; color 

 piceous-black, the head moderately impressed and punctate; pro- 

 thorax about one-half wider than long, narrowed before the middle, 

 the rounded sides subserrate, deplanate, subreflexed, densely, coarsely 

 and irregularly punctate; elytra oblong-oval, convex, posteriorly 

 subacute, the suture, margin and two costse on each elevated, with 

 transverse sinuous lines between them, more inflated in the female, 

 where they are twice as wide as the prothorax. Length 18.7-21.2 

 mm. Arkansas River, near the mountains. [Pelecyphorus 



sordidus Lee.] sordida Lee. 



A Similar in general to sordida but decidedly smaller and more ab- 



