6 COLEOPTERA OF NORTH AMERICA. 



characters of the tribes found in the United States may be thus 



expressed : — 



Gular suture distinct in all of our tribes. 



Antenna? inserted under frontal plates ; anterior tibiae palmate. 



VIII. Scaeitini. 

 Antenna? with the base free ; anterior tibiae not palmate. 2 



2 Mesosternum covered ; scutellum wanting. I. Omopheonixi. 

 Mesosternum visible ; scutellum distinct. 3 



3 Anterior coxal cavities closed behind by the prosternum. 4 

 Anterior coxal cavities open behind. 7 



4 Maxilla? covered at the base. VII. Peomecognathini. 

 Maxilla? exposed at the base. 5 



5 Prosternum produced behind. VI. Meteiini. 

 Prosternum not produced behind the coxa?. 6 



6 Antennae ordinary ; anterior tibia? slightly emarginate. II. Elapheini. 

 Antenna? verticillate, basal articulation prominent ; anterior tibia? strongly 



emarginate. III. Loeiceeini. 



7 Posterior coxa? attaining the margin of the body ; mesosternum not cari- 



nate. IV. Teachypachini. 



Posterior coxa? normal ; mesosternum carinate anteriorly. V. Carabini. 



Tribe I.— OMOPHRONINI. 



This tribe consists of but a single genus, remarkable for its 

 round convex form and the absence of scutellum. 



The head is broad, pointed in front; the labrum flat, the man- 

 dibles also flattened above ; the elypeal suture makes an angle 

 between the antenna?; the latter are filiform, with the four basal 

 joints smooth. The palpi are filiform. The mentum is deeply 

 emarginate, toothed in the middle, with the gular suture distinct; 

 the anterior coxse are surrounded by the prosternum, which is 

 broad, and prolonged behind so as to cover the mesosternum; the 

 side pieces of the latter are very transverse, and the epimera reach 

 inwards to the coxal cavity ; the episterna of the metathorax are 

 short and broad, without visible epimera. The striae of the elytra 

 are beyond the usual number ; in our species there are fifteen, 

 including the marginal. The anterior tibia? are obliquely sulcate 

 at the apex internally, one spine is apical, the other is placed 

 above the apex. The first joint of the anterior and middle tarsi 

 of the males is strongly dilated in our species, and covered with 

 hair beneath. 



The species are found in wet sand, near the margin of streams 

 or ponds; two are found on the Pacific, four on the Atlantic slope 

 of the continent. 



