AMERICAN COLEOPTERA. 271 



Base of thorax on each side squarely truncate, elytra with obsolete or feeble 

 striae. 

 Humeral margin of elytra not serrulate. 



Thorax longer than wide tenuis. 



Thorax as wide as long. 



Thorax small, not as long as the head and scarcely larger. Elytra obso- 

 letely striate, surface shining and with very short pubescence near 



the base pusio. 



Thorax larger and wider than the head. Elytra with scarcely any traces 

 of striae, its surface subopaque, finely alutaceous, not pubescent, 



eremita. 

 Humeral margin of elytra distinctly serrulate. 



Elytra subopaque, very finely alutaceous, surface with very feeble traces of 



striae. Thorax distinctly narrowed behind pubescens. 



Elytra shining, surface distinctly striate. Thorax rather transverse, scarcely 

 narrower posteriorly andai. 



In the above table I have attempted to arrange the species in such a 

 a manner as to indicate the gradual approach toward the forms of 

 Trechus existing in our fauna. The palpar structure of Tellkampfi 

 marks that species as the most specialized. The first three species in 

 the above table are also remarkable in their very feeble evidence of the 

 existence of the recurrent end of the sutural stria, it has, in fact, almost 

 entirely disappeared. 



A. Tellkampfi Erichs., Mull. Arch. 1844, p. 384. 



This species represents in our fauna A. Bilimeki, of Europe. It is 

 remarkable in having but two dorsal punctures. 



It occurs most abundantly in the Mammoth Cave of Kentucky, also 

 in Cave City cave. 



A. interstitialis Hubbard, American Entomologist, 1S80, p. 52. 



The characters given in the table sufficiently differentiate this species 

 from any other in our fauna. In it the recurrent sutural stria is feebly 

 indicated. It is also remarkable for the great length of the tarsal claws 

 which are a little more than half the length of the last tarsal joint. In 

 attempting to distinguish this species too great stress should not be laid 

 on the interatrial punctuation, as it is variable here and exists in an equally 

 variable manner in the next species. 



Occurs in the Mammoth and Cave City caves. 



A. Menetriesi Motsch., Etudes. Ent. 1862, p. 41. 



I find that Motschulsky quotes an earlier date for this species, but on 

 referring to the Etudes, 1854, p. 12, there is merely a mention of a spe- 

 cies. Three characters together serve to distinguish this species from 

 any other in our fauna — the serrulate humeri — deeply striate elytra and 

 prominent hind angles of the thorax. In the last respect, however, the 



