AMERICAN COLEOPTERA. 301 



larger than the eighth, and the antenna then approaches the structure 

 seen in Liodes. 



All the species are more or less contractile, some of them very 

 feebly so. In the first four species of the table the contractile power 

 is perfect, so that the specimens roll themselves into a very convex 

 lenticular mass with the legs retracted and completely concealed. The 

 greater the contractility the more arcuate the base of the thorax and 

 the humeri of the elytra more oblique. In all our species the base 

 of the thorax is foliaceous and overlaps the base of the elytra, but 

 Lacordaire says that the base of the one is sometimes applied against 

 the base of the other. 



Sexual characters other than those found in the tarsi do not occur 

 except in dentlgerum. In the males the tarsi are always 5 — 5 — 4, 

 and in the females 5 — -t — 4 or 4 — 4 — 4. Tlie last only occurs in the 

 group with prominent clypeus. 



Fourteen species are now known to us distributed in every part of 

 our territory, although the species do not have the extended range 

 observed in those of Anisotoma. A comparison of the number now 

 known with those described in the European lists suggests the proba- 

 bility of having but few additions to our lists in the future. 



Typical specimens of all the species excepting nniacoides and mandi- 

 hnlatum have been examined, the first being unnecessary while the 

 synonymy of the second seems quite evident. 



The following table will, I think, enable the known species to be 

 determined with ease, with the assistance of the descriptions, the 

 latter having in many cases been abbreviated by comparisons where 

 repetition seemed unnecessary. 



A. — Mesosternum continuous on the same plane with the luetasternum, moder- 

 ately seiJarating the middle coxse and subcarinate in front. 

 Body perfectly contractile, metasternum with an oblique ridge on each side, 

 limiting a shallow concavity for the reception of the front and 

 middle legs in repose. 

 Elytra polished, impunctate. 

 Third joint of antennae longer than the second. Posterior femora of 

 male simjjle. 



Larger species, sutural stria very fine oniscoides Beauv. 



Smaller species, sutural stria moderately impressed. ..exiguum Mels. 

 Third joint of antennae not longer than the second. Posterior femora of 

 male toothed near the tip. 



Small species, sutural stria wanting dentlgemm n. sp. 



Elytra punctulate, otherwise as in exiguum califoruionni n. sp. 



Body very imperfectly contractile, metasternum without raised oblique line. 

 Elytra substriate and punctate revolveiis Lee. 



