190 COLEOPTERA OF NORTH AMERICA. 



metnsternuru is obtuse in front ; the coxal plates are scarcely 

 toothed at the insertion of the thighs; the first joint of the tarsi 

 is not longer than the second; the sixth ventral segment is not 

 visible. 



Group II. — Plastoceri. 



The mandibles are thick at the base, toothed at the middle, 

 slender and curved at the tip, but embrace more or less closely 

 the labruni, which is on the same plane with the depressed front, 

 and closely connected with it, almost as in certain Cebrioninas. 

 The antennse are long and serrate in Aplastus; in the other 

 genera short, and pectinate with long branches in the males, in 

 the females serrate, and slightly pectinate; the prosternum- is 

 slightly lobed in Aplastus, not at all lobed in the other genera; 

 the sutures are double, slightly oblique, and not excavated ; the 

 middle coxeb are prominent, with the mesosternum acute in front; 

 the coxal plates are gradually and sometimes strongly dilated 

 inwards, and toothed at the origin of the thighs; the first joint of 

 the tai'si is as long as the two following united; the sixth ventral 

 segment projects beyond the fiftli, which is round at the apex. 

 In the female of Euthysanius, however, the elytra are short, the 

 wings wanting, and the abdomen greatly elongated ; the hind 

 coxaj also become so prominent, as to leave the genuine first 

 ventral segment (invisible in all other Elaterina?) free; following 

 this are the usual five equal to each other, t^hen the sixth, equal 

 to the fifth, but rounded at tip, and followed by a prominent 

 obtusely triangular seventh (really the eighth) ventral segment; 

 of these, all but the last two are margined behind with mem- 

 brane. 



AntonuiE long, serrate, 11-jointed. Aplastus. 



Antennje short, in the males pectinate ; 



Antermfe 11-jointed. Plastocerus. 



Antennae 12-jointed. Euthysanius. 



Sub-Pamil3- III.—CEBRIONIN.E. 



AntennEe distant at base, inserted under a frontal margin. 

 Mouth anterior; the labrum is transverse, connate with the front, 

 the suture usually distinct, sometimes obliterated ; mandibles 

 slender, prominent, and long, meeting beyond the labrum ; palpi 

 moderately long. Anterior coxte large, globose, without tro- 



