AMERICAN COLEOPTERA. 253 



Revision of tbe species ofCHIiAENIUS oftlie United States. 



BY GEORGE H. HORN, M. D. 



Durinji the present year (1876), there lias appeared an elaborate 

 monograph of the species of Chlaenlus by Baron Chaudoir, in the 

 Annali del Mus. Civ. di St. Nat. di Geneva, remarkable for its accu- 

 racy, perspicuity and evidences of great industry and analytical power. 

 With the exception of two all our species were known in nature to 

 him and these have been very accurately placed in his tables from the 

 descriptions alone, and when it is considered that more than four hun- 

 dred species have been tabulated, the magnitude of the labor becomes 

 apparent. 



There have been many new characters discovered and made use of 

 in the definition of groups and other divisions, so that Chlaenrus from 

 being one of the more difficult genera for study, has been rendered as 

 easy as it is possible to make one of such magnitude. 



From among our species Chaudoir has removed C. lithophilus, Say, 

 founding upon it a new genus BRAOHYLOBifS, characterized especially 

 by a peculiar conformation of mentum which will be spoken of here- 

 after. 



The true Chlaenius are divided into three groups as follows : 



I. — Abdomen at sides feebly or not at all punctulate, at middle smooth, 

 glabrous. 



II. — Abdomen punctulate, pubescent, middle usually smooth. ■ 

 III. — Abdomen punctulate over the entire surface, pubescent. 



The first group contains tomentosus and cumatilu^ the second prasi- 

 nus, cordicoUk^ leucoscelis and snlltarhis, while the third contains the 

 remainder of the species, divided into smaller groups by characters of 

 greater or lesser importance. 



It cannot be expected that Chaudoir's monograph will reach the 

 numerous students of our own country, and it has seemed to me 

 desirable that the results of his study should be more widely known, 

 and presented with such modifications as might seem desirable in re- 

 viewing the more limited number of species in our fauna. 



Having about one-tenth of the entire number in our fauna it might 

 be inferred that their arrangement would present less difficulty thaa 

 the whole number, this must be my apology for adopting an arrange- 

 ment entirely different from Chaudoir's, even after having spoken of 



