168 COLEOPTERA OF NORTH AMERICA. 



are double, straight or concave, and scarcely excavated in front ; 

 the coxal plates are suddenly dilated internally, with the angle 

 rounded, as in Drasterius, and a tooth at the origin of the thighs ; 

 the fourth joint of the tarsi is obliquely prolonged into a mem- 

 branous lobe. 



The genera JEolus and Heteroderes, as adopted by Candeze, 

 appear to be untenable, and heterogeneous, as already observed 

 by Duval ; I therefore continue to refer all of our species to 

 Monocrepidius, removing to Drasterius those with simple tarsi, 

 which were formerly included by me in the same genus. 



Group VI.— Dicrepidii. 



The strongly margined front, the prosternal sutures, excavated 

 in front, and concave outwards, and the tarsi with lobes beneath 

 the second and third joints, will distinguish this group. The 

 species are elongate, brown, hairy insects, with strongly serrate 

 antenna?, sometimes even pectinate in the males. The coxal plates 

 are strongly dilated inwards, and toothed. They are found in 

 the Southern States and Texas, and belong to two genera : — 



Mesostermim horizontal ; anterior part of front with two crests, uniting above 



with the frontal margin. Dicrepidius. 



Mesosternum oblique ; front not crested. Ischiodontus. 



To the latter genus belong Elater soleatus Say, Dicrepidius 

 ferreushec, and D. simplex Lee. 



Group VII.— Ludii. 



This group has the front convex, but not margined behind the 

 labrum ; the prosternal sutures concave outwards ; the tarsi simple, 

 pubescent beneath, and the posterior coxal plates less suddenly 

 dilated internally, but still distinctly angulated at the middle of 

 the hind margin, and strongly toothed at the insertion of the 

 thighs. The species are usually of large, though one species, 

 which I place in Ludius, is of moderate size; it is the Oregon 

 L. tartareus, formerly included by me in Elater. 



Our genera are three, thus distinguished : — 



Angle of the hind coxre acute, prominent ; 



Mesosternum declivous, not prominent. Ludius. 



Mesosternum protuberant. Orthostethus. 



Angle of the hind eoxze obtuse, broadly rounded. Crjgmus. 



