AMERICAN COLEOPTERA. 249 



species of Pntrohus (^sensu, Chaud.), in our fauna, are really variations 

 of one species, excepting longicnrnis^ Say. I can, therefore, hardly 

 see how there is room to insert two other species between those which 

 T have already placed toc^ether as synonyms. These two species are 

 ohfusiusculm, Chd., loc. cit., p. 43, Hudson's Bay, and stygicus, Chd., 

 p. 46, Newfoundland ; Lpcnntci^ Chd., p. 47, is suggested for rujipes, |] 

 Lee, and is unnecessary if the preceding remarks be correct. 



Our depressed species with quadrate thorax are placed by Chau- 

 doir, in a new genus. Platidiui^, seems to have value rather as a 

 sub-genus as rngicollis, Rand., is nearly intermediate in form between 

 the true Pdtrohus and Flatidhis. (g. li. H.) 



POCJOIVUS, Dej. 



This genus was first indicated in our fauna by Chaudoir, who in 

 the Rev. et Mag. Zool., 1868, p. 64, described a species from Texas, 

 (fexa.jius. Chd.) The essential differences between Patrohus and 

 Pogonus are, that the former has the head constricted more or less 

 behind the eyes, and the latter has the middle and posterior tarsi 

 sulcate above. 



Since Chaudoir, two other species have been published by Leconte, 

 paraUelus and depressiis, from Texas and California, respectively. 

 (Trans. Am. Ent. Soc, 1874, p. 44). 



In the review of the Pogonides above referred to, Chaudoir has 

 subdivided the Pogovus of older authors into five genera, bnsed on 

 characters which seem most too finely drawn to be generally admitted 

 as valid. 



By the method of division followed by Chaudoir, our three species 

 belong to different genera, the characters of which will be given 

 below. It seems to me entirely unnecessary to multiply genera on 

 such small differences, and science will be equally benefitted by indi- 

 cating sub-generic groups without the burden of additional names. I 

 therefore prefer to consider our species as constituting one genus, 

 with three groups in our fauna. 



The three genera above mentioned are as follows : 

 Mentum tooth deeply notched ; ligula with a single bristle at tip. 



Epilobes of mentum acutely toothed POGONUS. 



Epilobes of mentum obtuse POGONISTES. 



Mentum tooth shorter and broader, feebly eniarginate; ligula bisetose at tip. 



Epilobes of mentum obtuse DIPLOCHiETUS. 



PoGONUS as above defined has in addition the following characters : — 

 Elytra with distinct basal marginal line, scutellar stria and three punc- 

 tures on the outer side of the third interval. 



TRANS. AMER. KNT. SOC. V. (32) DECEMBER, 1876. 



