484 



CASEY 



segment much feebler, almost obsolete. Length 3.9-4.3 "^"i- 5 

 width 1 .18-1.6 mm. California (Humboldt Co.) . . .nucleatus Csy. 



Both of these species are represented before me by large 

 series, but I have not recognized any external secondary sexual 

 characters. The great extension of the prosternum before the 

 coxae and its pronounced tuberculose sculpture, similar to that 

 of the upper surface, while the entire remainder of the under 

 surface is simply punctate, is a rather noticeable character of 

 the genus. 



Tribe Ar^oschizini. 



In this tribe and the Stenosini, with which it is usually con- 

 founded by reason of the general form of the body and antennae, 

 the fifth ventral segment loses the very peculiar transverse 

 excavation characterizing the three preceding tribal groups and 

 becomes unmodified, its surface corresponding with the general 

 convexit}'' of the abdomen ; it is rounded behind and a little 

 shorter than the two preceding combined, but, it should be re- 

 marked, there is also an entirely different peculiarity of the 

 abdomen in the present tribe, the third suture being very strongly 

 sinuate and notably more strongly so than the fourth. The 

 tribe resembles the Stenosini in the small size and elongate, 

 moderately convex form of the body, thick perfoliate setose or 

 squamose antennae and some other characters, but differs in the 

 complete absence of elytral epipleuras, as in the three preceding 

 tribes, these being very well developed in the Stenosini, in the 

 presence of elytral ridges, which are wanting in that tribe, and 

 in the much larger mentum, concealing the entire Hgula. With 

 the Adelostomini, however, it is very much more closely allied, 

 differing in its smaller mentum, exposing the maxillae at the 

 sides, the maxillie being completely concealed but the ligula 

 uncovered in that tribe, and in the very small terminal joint of 

 the antennee, but resembling it in the absence of elytral epi- 

 pleurae and presence of dorsal ridges. We have but a single 

 genus as follows: — 



Form elongate, moderately convex, the hind body pedunculate, moder- 

 ately inflated, elongate-oval, without humeral angles, the hind 

 wings wanting; head elongate-oval, the clypcus very large, as 

 long as the entire remainder but not separated by a transverse 

 suture, the lateral oblique impressions deep, the lateral lobes very 



