AMERICAN OOLEOPTERA. 275 



C neTadense n. sp. — Oblong-oval, feebly convex, not broader in front, 

 piceous to ferruginous, finely pubescent. Head rather finely punctured. Au- 

 tenniB ferruginous, club darker, attaining the middle of the thorax, the club 

 four-jointed, the terminal joint a little larger than the tenth, obtuse at tip 

 and paler. Thorax one-half wider than long, sides moderately arcuate and 

 gradually narrowed to the front, base truncate, hind angles rounded, surface 

 finely and not very densely punctulate. Elytra as wide as the thorax, sides 

 moderately arcuate and gradually narrowed to apex, sutural stria entire, finely 

 impressed, surface moderately densely punctured and a very little more coarsely 

 than the thorax. Abdomen finely but not densely punctulate, metasternum at 

 sides coarsely punctate. Length .06 — 08 inch ; 1.5 — 2 mm. 



Male. — Anterior tibiae straight very little broader at tip, the spurs lobed at the 

 side, the tarsi slightly dilated. Middle and posterior tibiae straight, the tarsi 

 slender, slightly compressed. Posterior femora without tooth. 



Female. — Anterior tibiae straight, spurs simple, tarsi filiform. Otherwise as 

 in the male. 



This species bears such a very close superficial resemblance to 

 celatum before described, that it is impossible to distinguish them 

 except by the male characters which are fortunately very evident. 



Occurs in western Nevada, (Morrison). 



Tribe V. — Anisotomini. 

 Anterior coxae conical, prominent, contiguous, with trochantin, the cavities 

 strongly angulate externally and narrowly closed behind. Middle coxae always 

 separated but in some narrowly. Posterior coxae contiguous. Abdomen with 

 six segments subequal in length or with the first a little longer, the sixth 

 usually very short. Antennae variable in the number of the joints either ten 

 or eleven, club variable of 3 — 4 or five joints; arising under a slight frontal 

 margin in all of the genera. 



By a comparison of the above formula with that of the Silphini 

 it will be seen that they differ only in the structure of the prothorax 

 beneath. In all preceding reviews of the tribe the structure of the 

 posterior trochanters has been made use of in a manner which seems 

 entirely false and misleading. I do not find any constant difference 

 between the two tribes in the form of the trochanter, on the contrary 

 there are forms in each which if rigorously interpreted would remove 

 their possessors from the respective tribes. In proof I need only cite 

 Pteroloma of the Silphini and certain Hydnobius in the present tribe. 

 Taking the tribe Silphini as recognized by Lacordaire and his fol- 

 lowers, the entire series which I have here separated as Cholevini 

 do not differ materially from the present tribe in the form of the 

 trochanter, but are quite at variance with that found in the larger 

 Silphini. 



As a rule any part of an insect which exhibits a decided tendency 

 to vary, not only between species but also in the two sexes, is an 



