CARABIDAE. 21 



and thorax, three groups may be formed, which are, however, 

 merged together by certain foreign genera. 



Head rhomboid al, with a narrow neck ; thorax cylindrical. Casnonije. 

 Head rounded ; thorax convex cordate, pedunculated. Lacunophori. 



Head not narrowed behind ; thorax flat, ovate. EucjEri. 



Group I. — Casnoniae. 



The large rhomboidal head, narrow thorax, and truncate elytra, 

 •enable this group to be known at first sight. We have in it the 

 first occurrence of bilobed fourth joint of tarsi, and (in foreign 

 genera) of serrate ungues, characters recurring afterwards in other 

 tribes. The species are small, and found under stones; Leptotra- 

 chelus also on plants. They fly at night, and are attracted by 

 lamps into houses. One species of Casnonia occurs in California, 

 and two in Atlantic America; one Leptotrachelus in the Atlantic 

 region. 



Tarsi filiform. Casnonia. 



Tarsi with fourth joint bilobed. Leptotrachelus. 



Group II. — Lachnophori. 



The head is large and rounded; the thorax small, cordate, con- 

 vex, and turned into a peduncle at base. The elytra broadly 

 rounded at tip, the ungues always entire. 



The species are small insects, living in the mud near water- 

 courses, and are gregarious. One species of each genus is found 

 in the southern part of the Atlantic district, and another in the 

 valley of the Colorado and Gila. Ega is remarkable for the outer 

 joints of the antennas being white, and the elytra with several deep 

 grooves extending from the base to the middle. In both of our 

 genera the last joint of the palpi is ovoid, and sharply acuminate 

 at the apex. 



Head strongly contracted behind. Ega. 



Head slightly contracted behind. Lachnophorus. 



This group osculates so completely with the Fterostichini that 

 no distinctive character can be given, except that the three basal 

 joints of the antennas are not entirely glabrous. But no doubt 

 can result in the mind of the student of our fauna, since the oscu- 

 lant forms are all foreign. 



