300 AMERICAN PACHYBRACHYS (cOLEOPTERa) 



of elytral punctures possesses quite a distinct facies, there are 

 really scarcely any constant taxonomic characters by which they 

 maj^ be separated. The prosternal character given in the Le- 

 Conte & Horn Classification is not constant, and that given by 

 Suffrian — ''prosternum sulcate" in Pachybrachys and "feebly 

 longitudinally tumid at middle in Grihurius" is open to the same 

 criticism. In the rather slender material in Grihnrius in my own 

 collection, including five native species, I note that the tibiae are 

 completelj'- unarmed at tip in the males of all species, and in 

 both sexes of some. Whether or not this holds true in the numer- 

 ous Mexican species I know not, but the character may be useful 

 in our own fauna at least. The following table presents the 

 characters observed for separating the three genera in question. 



Prothorax not margined at base, the edge finely crenulate; anterior margin of 

 prosternum prominent at middle, the intercoxal process impresso-emarginate 

 at tip with more or less sharply prominent angles; front thighs not incrassate, 

 tibiae without terminal spurs. Cryptocephalus 



Prothorax margined at base, the edge not crenulate ; anterior margin of proster- 

 num sinuate at middle, intercoxal process not emarginate at tip ; front thighs 

 incrassate (except hepaticus group). 



Prosternum often flat or feebly tumid along the median line, intercoxal 

 process longer, cordate pointed, the angle narrowly rounded; all tibiae 

 unarmed in the c?- Griburius 



Prosternum sulcate, intercoxal process less produced, the apex more ob- 

 tusely but more sharply angulate; middle tibiae with terminal spur in both 

 sexes (except hepaticus group). Pachybrachys 



Review of Structural Characters Useful in Taxonomy 



In order to avoid a considerable amount of circumlocution and 

 useless repetition in the systematic part of the work, it will be 

 profitable before proceeding to the tables and specific descrip- 

 tions to pass in review the various parts of the body, pointing out 

 those characters which are of value in the separation of species, 

 as well as those which from their universality or individual 

 variability are of little use in this respect, and may therefore in 

 great part be omitted from the descriptions. 



General form. — The form of body throughout the genus does 

 not vary greatly and may be dcs('ril)ed as short, compact, sub- 

 cylindrical. The ratio of length to width averages about 100 to 

 56, varying, according to measurements made, from 100 to 48 

 in a particularly slender male of sobrinus, to 100 to 63 in an 



