AMERICAN COLEOPTERA. 155 



17. Metasternum deeply excavate in front; ventral punctuation annulate. 



Coelostetlius. 



18. Metasternum deeply abruptly excavate; ventral segments comlate. the punc- 



tures annulate ; elytra punctate-striate Trypopitys. 



Metasternum moderately deeply, less abruptly excavated ; ventral segments 

 free, punctuation simple; elytra irregularly punctate. 



Colposternus. 



A€TENOBIUS new genus. 



This name is proposed for a small number of Californian species 

 which strongly resemble a very slender Oligomerus — notably 0. 

 sericann—hxxt differ radically in antennal formation, these organs 

 being rather feebly serrate, with joints 3-10 of nearly equal length ; 

 second joint short, oval ; eleventh nearly linear, a little longer than 

 the tenth. The palpi are nearly as in Oligomerus sericans, the first 

 joint short; second and third obconical, the former more elongate, 

 the latter about as wide as long; terminal joint elongate, pointed. 

 The prosternum is rather short before the coxa?, the front and mid- 

 dle coxse contiguous. Tarsi distinctly narrower than in Oligomerus, 

 the first joint as long as the next three or very nearly so, second 

 joint equal to the third and fourth united, the latter short and fee- 

 bly or scarcely emarginate at apex ; last joint about twice as long as 

 wide, moderately dilated apically. The pubescence is very short, 

 moderately inclined; the elytra feebly striate- punctate. First, sec- 

 ond and fifth ventral segments nearly equal, third and fourth sub- 

 equal but a little shorter. 



The only other genera in this tribe having somewhat similar an- 

 tennae are Trypopitys and Colposternus, but they are not otherwise 

 allied very closely, the front and middle coxse being widely separa- 

 ted and the metasternum excavated in front. Euceratocerus is, how- 

 ever, very closely related in most respects, except antennal forma- 

 tion ; indeed, the three species for which the present genus is estab- 

 lished were referred by Casey to that genus. 



As only a single species is known to me the following table is 

 necessarily based on Casey's descriptions: 



Pleural sulcus below the humeri deep and strongly marked; eyes separated by 



more than three times their own width 1. pleiiralis. 



Pleural sulcus narrow and feeble. 



Elytra fully twice as long as wide; eyes small, separated by fully four times 



their own width 2. macer. 



Elytra much shorter, three-fourths longer than wide; eyes more convex and 

 better developed, separated by three times their own width. 



3. saginatus. 



TRANS. AM. ENT. SOC. XXXI. MAY, 1905. 



