298 COLEOPTERA OF NORTH AMERICA. 



of our genera, though always deeply emargiuated, and embracing 

 the antennal tubercles. 



Group I.— Oemea. 



The ligula is more or less corneous, and usually only emargi- 

 nate at tip ; though in Achryson, corneous, with the front part 

 membranous, and broadly bilobed ; the body is slender and elon- 

 gate, the palpi frequently very unequal, the antenna? usually long, 

 and longer than the body in % ; the eyes are usually very large, 

 convex, coarsely granulated, and very deeply emarginated. The 

 thighs are rather slender, except in Gracilia, where they are 

 strongly clavate. 



Three sub-groups are indicated, 



Epimera of niesothorax large ; 



Front trochantins very distinct. Oemes. 



Front trochantins not visible. Achrysones. 



Epimera of niesothorax small. Gracilis. 



Sub-Group 1 . — emes. 



Oeme rigida (Say), from the Middle and Southern States, and 

 two new genera, Ganimus, and Eucrossus from Arizona, repre- 

 sent this sub-group in our fauna ; they are pale brown, slender 

 insects, with the antennae hairy beneath ; rough with small acute 

 tubercles on the under surface of the 3d, 4th, and 5th joints in 

 Oeme ; these joints in Eucrossus are not rough, but are armed on 

 the inner side with a terminal spine ; the presternum is very nar- 

 row and prolonged in Oeme; moderate in width in Eucrossus: 

 the mesosternum is narrow in Oeme and Ganimus, wider and trun- 

 cate in Eucrossus ; the palpi are dilated in the latter two, but 

 scarcely so in the former, very unequal in all.* The prothorax 

 is strongly constricted at base in Oeme, but in Ganimus is trans- 

 verse, more rounded on the sides, and not constricted at base. 



The sculpture of the prothorax of the % in Eucrossus is pecu- 

 liar ; finely alutaceous, opaque, with a smooth dorsal vitta, and a 

 large scar-like mark each side, nearly parallel with the dorsal 

 line, commencing near the base, suddenly inflexed just in front 

 of the middle, and then abbreviated. 



* Lacordaire, 1. c. viii, 222, says that the palpi are subequal in Oeme, 

 but his specimen seems to have been much mutilated. 



