LECONTE— SYNOPSIS OF PTEROSTICHUS. 235 



under the particular groups in which they occur. The following table will express 

 the relation of the groups among themselves. 



A. Margine elytrorum bistriato. 



B. Margine elytrorum unistriato. 



1. Thorax tenuiter marginatus ; parapleurse breves. 



a. Elytra punetis dorsalibus nullis. Sp. 1 — 17. 



b. Elytra bipunetata. Sp. 18. 



c. Elytra tripunctata, stria scutellari distincta. Sp. 19. 



d. Elytra tripunctata, stria scutellari nulla. Sp. 20 — 21. 



2. Thorax tenuiter marginatus ; parapleurse longse. 



e. Thorax basi. unistriatus ; elytra tripunctata. Sp. 22 — 28. 



f. Thorax basi bistriatus ; elytra tripunctata. Sp. 29 — 32. 



g. Thorax basi unistriatus ; elytra 5-punctata. Sp. 33 — 34. 



3. Thorax fortius marginatus. 



h. Thorax basi bistriatus ; elytra bipunetata. Sp. 35 — 38. 



i. Thorax basi foveatus ; elytra bipunetata. Sp. 39. 



k. Thorax basi foveatus ; elytra 4-punctata. Sp. 40. 



1. Thorax basi foveatus ; elytra irregulariter striata. Sp. 41. 



m. Thorax basi bistriatus ; elytra tripunctata. Sp. 42 — 44. 



A. 



None of the species of this genus are found in North America ; they may be 

 divided into several groups, such as Abax, Molops, &c, according to the form of the 

 thorax. Feronia quadricollis LeConte, An. Lye. 4, 343, does indeed belong here, but 

 it is no American insect, and is identical with Pterostichus parallelus of Europe. 



a. 

 * We have here a large number of species, usually of a slender form, with the thorax 

 quadrate and gradually narrowed behind ; the margin of the elytra is moderate and 

 has but a single stria; the elytra have no dorsal punctures; the parapleurse are 

 short. For the better determination of the species, which are frequently very closely 

 allied, this group may be subdivided : 



a. Thorace basi immarginato. Sp. 1 — 9. 



/3. Thorace margine basali medio interrupto. Sp. 10 — 15. 



y. Thorace basi tota marginata. Sp. 16 — 17. 



a a- 



The thorax is trapezoidal, narrowed behind, the posterior angles distinct, not promi- 

 nent ; the basal impression is linear and single except in the two first species in which 

 there is a short outer impression, margined in the first by a very faint carina ; the 

 base is entirely without a marginal line. The anterior tarsi of the males are variable 

 • 



