SILPHIDAE. 81 



Groiiii I. — Platycholei. 



This group contains Plalycholeus leptinoidcs, au oval, de- 

 pressed, testaceous species found in California and Nevada. It 

 seems to be our closest approach to Bathyscia. 



Group II. — Cholevae. 



The species of this group are of small size, oval form, usually 

 narrower i)osteriorly, the surface finely pubescent, the elytra 

 usually transversely strigose, rarely punctured. 



The genera are as follows: — 



Mesosternum not cariuate, the middle coxae contiguous, last joint of maxil- 

 lary palpi as long as the preceding. 



Antennae serrate; tibial spurs moderate, simple. Catoptrichus. 



Antennae gradually clavate. 



Tibial spurs moderate in length, simple. Choleva. 



Tibial spurs very long, bipectinate. Prionoch^ta. 



Mesosternum cariuate, coxie separated ; last joint of maxillary pal])i short. 

 subulate. 



Antennae gradually clavate, not longer than the head and thorax ; eyes 

 well developed ; mesosternal carina moderate. Ptomaphagus. 



Antennae slender, longer than the head and thorax ; eyes small ; meso- 

 sternal carina prominent. Adelops. 



Catoptrichus, Prionochaota, and Adelops seem peculiar to our 

 fauna, the first occurs in .Alaska, the second in the Atlantic 

 region. Adelops occurs in the caves of the central region, and 

 has been erroneously described as eyeless. Choleva and J*toma- 

 l)hagus occur also in Europe, and are represented on both sides 

 of our continent. 



Group III. — Colones. 



In our fauna but one genus, Colon, constitutes this group. 

 The species are small, oval, narrower behind, the surface punc- 

 tured and finely pubescent ; they occur on both sides of the con- 

 tinent. 



Tribe v.— AlVISOTOIWIIVI. 



Body oval, convex, sometimes hemispherical, sometimes capa- 

 ble of being contracted into a ball. Anterior coxae conical, 

 prominent, contiguous, with trochantin, the cavities strongly 

 6 



