40 AMERICAN COLEOPTERA. 



1. B. IfeTigatuin Say. — Form robust, convex ; color dark green or bronze' 

 very shining. Head slightly narrower than the thorax at apex ; palpi testaceous; 

 antennfe about one-half as long as the body, fuscous, the basal joints testaceous. 

 Prothorax subquadrate, slightly wider at base than apex, more than one-half 

 wider than long, with a few sparsely placed punctures at base ; apex feebly emar- 

 ginate; median line tine, entire or abbreviated in front; transverse impressions 

 moderately distinct; basal impressions broad, deep, bistriate, the outer stria 

 small ; sides with the margin distinctly reflexed, arcuate in front, at most obso- 

 letely sinuate in front of the hind angles, which are subrectangular and carinate. 

 Elytra less than one-half wider than the thorax, oblong-oval ; intervals feebly 

 convex. Beneath nearly black, shining. Legs rufo-testaceous, the femora often 

 slightly darker. Length .22-. 29 inch ; 5.5-7.25 mm. 



An aberrant species, very distinct from the others of the genus. 

 In fact, LeConte erected the genus Hydrium for its reception (Ann. 

 Lye, 1848, iv, p. 453), but later reunited it with Bembidium, from 

 which it does not seem sufficiently distinct for generic separation. 

 It has usually been placed near the end of the genus near B. semi- 

 striatum, with which it has little in common, however, except the 

 arrangement of the dorsal punctures and the abbreviated elytral 

 strise. On the other hand it is allied to B. nitidum by the bifid 

 mentum tooth and the subangulate elytral humeri. I have accord- 

 ingly placed it at the head of the genus. It is subject to but slight 

 variation. In well preserved specimens the setje, arising from the 

 rows of punctures on the elytral intervals are very distinct. 



It is widely distributed, occurring locally from Nejw ^Hampshir e 

 to Montana and Texas, specimens having been seen from the three 

 States mentioned and from Pennsylvania, South Carolina. Illinois, 

 lowaj Missouri and Kansas. 



Group ii. nitidum. 



Maxillse with the outer lobe bi articulate ; mentum with a short 

 bifid tooth ; frontal grooves single, parallel ; eyes moderately large 

 and prominent. Thorax truncate at base, scarcely obliquely so each 

 side. Elytra with the outer striae abbreviated behind, the eighth 

 distinct from the margin ; humeri subangulate ; third interval with 

 two dorsal punctures. 



This group seems in some respects intermediate between the last 

 and the next two. The bifid mentum tooth and abbreviated outer 

 striae of the elytra ally it to the former, while to the littorale and 

 coxendix groups it is related by the number and position of the dorsal 

 punctures. With all three it agrees in having the humeri of the 

 elytra subangulate. 



