AMERICAN PHILOSOPHICAL SOCIETY. 579 



Length under one fifth of a inch. 



Allied to A. hrunneus nob., but the segments of the tergum 

 are not margined around by dusky ; on each is a dusky triangle, 

 much dilated on the posterior margin, so as nearly to reach the 

 lateral edge. 



OMALTUM Grav. 



1. 0. MARGINATUM. — Piceous, punctured ; antennae and feet 

 dull rufous. 



Inhabits upper Missouri. 



Body oblong-oval, piceous, punctured ; head, punctures sparse, 

 obsolete at tip, with an indentation each side between the an- 

 tennas and a longitudinal impressed line each side at base ; an- 

 tennae rufous at base, red bi'own obscure attip with cinereous 

 hair; palpi rufous; thorax transverse sub quadrate, punctures 

 not crowded ; posterior edge obscurely piceous ; elytra longitudi- 

 nally quadrate, covering more than half of the tergum, exterior 

 margin piceous towards the humerus; exterior hind angles 

 rounded, sutural ones acute ; almost to be traced into striae ; feet 

 piceous, paler towards the tip ; tergum obscurely rufous on the 

 margin, and on the posterior margins of the segments. 



Length one-tenth of an inch. 



I obtained this insect when with Major Long's expedition to 

 the Rocky Mountains ; I think it occurred at Engineer Canton- 

 ment on the Missouri. [464] 



2. 0. ROTUNDICOLLE. — Piceous, black; thorax rounded be- 

 hind, emarginate before. 



Inhabits Pennsylvania. 



Body with rather large, numerous and profound punctures ; 

 antennae piceous, brown, the three basal joints, labrumand palpi 

 honey-yellow ; thorax transverse oval, deeply emarginate before, 

 equally punctured ; posterior angles rounded ; edges piceous ; 

 elytra equally punctured, long ; terminal edge piceous ; tergum 

 piceous, rather paler on the posterior margins of the segments ; 

 feet dark honey-yellow; venter somewhat piceous. 



Length less than one-fifth of an inch. 



Taken on the wing at twilight, in October, 



[Belongs to Olophrum Er. — Lec] 

 1834.] 



