AMERICAN COMPONENTS OF THE TENTYRIIN^ 433 



the dorsal teeth as usual, the apex feebly, very unequally bifid, 

 with the upper lobe broad and truncate, nearly as in Triorophus 

 but with the outer side concave toward base ; epipleuree sub- 

 equal in width throughout, the met-episterna rather wide. 

 [Type O. villosa n. sp.] Oxygonodera 44^/ 



7 — Body larger than in the three preceding genera, subglabrous to 



sparsely pubescent, the elytra with even and entire series of con- 

 spicuous punctures ; eyes emarginate anteriorly, not prominent; 

 mandibles acutely and deeply bifid, the two lobes unequal, both 

 acutely rounded, the outer surface concave at base only; elytra 

 rather less inflexed beneath than usual, the epipleuras broader, 

 especially toward base, the met-episterna moderately narrow. 

 [Type T. perforatus Lee] Triphalus /«/^ 



8 —Form nearly as in Triphalus^ the elytra with similar regular and 



entire series of coarse and conspicuous punctures ; size relatively 

 large as in Triorophus ; tarsi pubescent and spinose beneath; 

 eyes rounded, feebly emarginate anteriorly; mandibles without 

 tooth on the upper surface — fide Horn. \^y^e S. puncticolh's . 



Horn] Stibia '^^^ 



In the structure of the front this tribe presents the same diver- 

 sity as the Trimytini or the palgearctic Gnathosiini, comprising 

 forms with prominent quadrate epistoma or a shorter and more 

 triangular form of that part. The last five genera of the above 

 table are related in this respect to Triorophus, in precisely the 

 same way that the Mexican Pcsccnnius, of Champion, is related 

 to the other genera of the Trimytini, the only very important 

 difference between these two tribes apparently being the strong 

 inferior inflexion of the elytra in Triorophini and the absence 

 of this character in the Trimytini ; in the former, also, the pro- 

 thorax is generally strongly narrowed to the base, while in the 

 latter it is usually narrowed from the base forward, the chief 

 exception being Chilometopon. The principal distinguishing 

 character between the two tribes in question and the Euryme- 

 toponini, which is also diversified to a considerable degree in 

 the form of the front, is the fact that in the former the man- 

 dibles clasp or rest upon the epistomal lobe when closed, while 

 in the latter tribe they slip entirely under the lobe, but in both 

 cases they grasp and retract the labrum, either by a single tooth 

 or by a tooth on each mandible, the latter being the usual con- 

 dition in the Triorophini. The present tribe does not seem to 

 include any of the Central American genera recently described 

 by Champion, all of which may be readily assigned either to 

 the Eurymetoponini or Trimytini. 



