AMERICAN COLKOPTERA. 169 



CTE\OBIUN LeConte. 



Body slender, cylindrical, prothorax deeply excavated beneath 

 for the reception of the head, which is received in repose upon the 

 anterior coxa?. Antennae 11 jointed, first joint thicker, nearly cyl- 

 indrical ; second smaller and shorter; third equal in length to the 

 second, triangular, about as broad as its length in the female ; 

 fourth to eighth transverse, with the outer angle acutely prolonged 

 in the female, the fifth and seventh more prolonged than the others. 

 In the male the third to eighth joints are prolonged externally into 

 a cylindrical branch twice as long as the joint itself; the ninth and 

 tenth joints are compressed, elongate-triangular, each longer than 

 the two preceding; the eleventh joint is elongate oval and com- 

 pressed ; ninth to eleventh joints united, nearly as long as all the 

 preceding joints. Presternum rather short before the coxae, which 

 are distinctly separated by the prosternal process, the latter parallel 

 between the coxa? then suddenly acuminate at tip. Middle coxae 

 narrowly but clearly separated by the meso and metasternal pro- 

 cesses. Metasternum deeply channeled behind ; hind coxal plates 

 narrow, nearly parallel, not dilated inward. Tibiae slender, not 

 compressed; tarsi longer than the tibiae, narrow, first joint elongate, 

 last joint short, dilated ; claws slender. Abdominal segments free, 

 one to four subequal, fifth nearly as long as the third and fourth 

 together, the tip conical and prominent in both sexes. Last joint 

 of both maxillary and labial palpi moderately elongate and obtusely 

 subtruneate at tip. 



The above diagnosis with some slight additions and corrections is 

 a transcription of LeConte's original description. One species only 

 is known. It bears a rather strong resemblance to certain species 

 of Hadrobregmus and Oligomerus, but is at once distinguished by its 

 antennal and abdominal formation. 



The Ctenobium cinereum of Horn is not congeneric with antenna- 

 turn; for it and several other closely allied forms the genus Xercmo- 

 bivm has been established — see page 159. 



1. C aiiteniiatum Lee. — Cylindrical, brown, with sparse, fine, very short 

 recumbent pubescence. Head (% ) nearly as wide as the prothorax; eyes large, 

 the front but little wider than their vertical diameter. Prothorax scarcely as 

 wide as the elytra, side margin narrow, feebly subserrate, front angles nearly 

 right, hind angles not defined, disk subconically elevated at middle, the eleva- 

 tion divided by a feeble longitudinal channel. Elytra striate, stria punctate 



TRANS. AM. ENT. SOC. XXXI. (22) MAY, 1905. 



