232 MEMOIRS ON THE COLEOPTERA 



Prionus Geoff. 



A study of the American species of this genus, which with the 

 Prioninse in general are very much more developed and diversified 

 than in the palsearctic fauna, reveals an unanticipated variety of 

 structure, which renders a satisfactory taxonomic arrangement of 

 them much less difficult than is usually assumed. The species 

 and subspecies are numerous and can be segregated into the three 

 following very evident subgeneric groups: 



Antennae 12-jointed in both sexes, imbricate (cf ) or slender and serrate 

 (9), the serratures on the inner sides of the apices of the joints. 



Group I 



Antennae (cf ) having from about 14 to about 19 joints, usually with one 

 or two less in the female than in the male, the joints, except the 

 terminal, formed in both sexes nearly as in group I Group II 



Antennae (o 71 ) with 28 to 32 joints, very stout, closely imbricated and 

 greatly developed, or ( 9 ) much shorter and slender, having notably 

 fewer joints and with the outer joints short, transverse and not 

 asymmetric as in the two preceding groups but bilaterally symmetric. 



Group III 



The first group is distributed abundantly from the Atlantic to 

 the Pacific, but apparently does not extend far into Mexico; the 

 second extends from the Atlantic to the Sonoran regions but does 

 not enter the true Pacific fauna, while the third, generally rare in 

 individuals and apparently comprising but few species, is confined 

 to Texas and adjacent regions. 



Group I. 

 Prionus in sp. 



The very numerous species and subspecies of this group may be 

 distinguished by the following structural characters: 



Eyes with a very large emargination which extends more or less nearly 

 half way through them, the inner part of the eyes less full or shorter 

 antero-posteriorly, the head generally larger, frequently swollen 

 behind the eyes; color black or blackish as a rule, the metasternal 

 pubescence less developed or wanting medially, especially in the 

 female; male usually much smaller than the female 2 



Eyes with a relatively smaller and shallower emargination, which never 

 extends so deeply, the inner part of the eyes fuller; head never not- 

 ably swollen at base; color never black; metasternum always pubes- 

 cent throughout in both sexes 1 1 



2 Antennal joints (d*) only very feebly or barely at all sinuate at their 

 apices beneath; body more oblong, very obtuse behind, the pro- 



