71 



render it somewhat difficult to locate some of the genera; /or example, 

 Oxijcoryphus, Clinj.toc]t}Xion,anA most of the species of Stenohollirus have the 

 face somewhat oblique, and in general appearance approach Opomala and 

 Pyrgomorpha; but tVoni the former they are at once distinguished by the 

 absence of the prosternal spine, and from the latter by the less oblique and 

 straight or sub-convex face and by Ihe form of the antennae; Ijut in regard to 

 the last character, the distinction between Pyrgomorpha and Oxycoryphiis is 

 slight. In the slo]>e and shape of the head and form of the thorax, Cliryso- 

 cJraon makes the nearest approach (of the United States genera) to 

 Pyrgomorplia; the Stenohothri in general appearance approach Opomala. 



The following are the United States genera belonging to this group, 

 placed in what I conceive to be their natural order, considered as descending. 

 It will be observed that I take the diminishing obliquity of the face and 

 increasing convexity of the vertex as my chief guides in this arrangement: 



Oxycoryphus, Chrysochraon. Acrolophitus, Pedioscertetes, Stenobothnis, 

 Gomphocerus, Stetheophyma, Tragocephala, Tomonotus, ffidipoda, Tropido- 

 lophus, Staurouotus, Boiipedon, Brachypeplus. 



This group admits of two tolerably well-marked sections, depending 

 chiefly upon the direction of the face and form of the pronotum. 



In order to aid, as far as possible, in locating species in the genera to 

 which they belong, I add the following table of the genera of this group, 

 which gives the charactei's a little more fully than in the general table which 

 • stands at the commencement of the family, and which is somewhat differ- 

 ently arranged : 



Synoptical table of the genera. 



A. Prosternuin smootli, uot tubereulate : 



a. Vertex asceudiug iu front of the eyes iu the form of a coue or 

 triaDgular pyramid, pointing obliquely forward and upward : 



h. Median carina of tbe pronotum minute on the anterior and mid- 

 dle lobes, but elevated into au arcuate crest on the posterior 

 lobe Acrolophitus. 



hh. Median carina of the pronotum minute throughout ; no part 



elevated Pedioscertetes. 



an. Vertex horizontal or deflexed : 



h. Face oblique, straight : 



c. Hind border of the pronotum truncated . Chrysochraon. 



cc. Hind border of the pronotum produced into an obtuse or acute 



angle : 



d. Anteiuitx? very short, scarcely longer than the head, somewhat 



enlarged and flattened near the base O-njeoryphus. 



