NATURAL SCIENCES OF PHILADELPHIA. 3 



With this object in view, I sought the divisions established by Jacquelin Du 

 Val, in his admirable treatise " De Bevibidiis Europacis"* among our own species, 

 but was much disappointed to find them not at all applicable. After repeated 

 trials to reduce a system on the characters of Du Val, which should present a 

 natural series when applied to the species before me, I was at length com- 

 pelled to adopt another method of division, the result of which is presented 

 below. 



But first with regard to the limits of Ochthedromus Lee. and its claims to re- 

 gard as a natural genus. European entomologists have thus far refused to place it 

 in their system, adhering to the view that the subulipalpate Carabica, with few 

 exceptions, (Anillus is received by all, Thalassobius and Tachypus by a few) 

 form but one great genus Bembidium. From this view I ventured to dissent 

 many years ago, but more distinctly in ray notes on the classification of the 

 CarabidiB of the United States,* where the Trechi and Berabidia were widely 

 separated on a difference in the mesothoracic parapleurae ; these in the former 

 are divided by a suture near the posterior margin, and in the latter by a 

 diagonal suture. I also found that in the Trechi the marginal stria of the elytra 

 was interrupted at the middle, while in the Bembidia it was entire. Renewed 

 observation has confirmed the result then obtained, and has induced me still 

 farther to enlarge the group of Trechi, by adding to it not only Tachys, but 

 also Anillus, the form recognized by me as Blemus, (which is probably not 

 genuine Blemus), and Lymnaeum, which has been found on the coast of Cali- 

 fornia, at San Diego. 



Thus of the genera in my table (loc. cit. 39'7) there remains only Pericomp- 

 sus, Bembidium, Octhedromus, Hydrium,''and Patrobus. The last named genus 

 must form a group by itself, or at least separate from Bembidium, and more 

 nearly allied to Pterostichus, or Platynus. Hydrium does not appear to be suf- 

 ficiently definite to be retained. 



Of the three genera thus retained, Pericompsus is known by the antf.rior 

 tarsi of the male being hardly or not at all dilated, by the anterior tibiae being 

 obliquely truncate at tip, and by the elytra being without scutellar strije : the 

 mentum tooth is small and acute. Bembidium and Ochthedromus differ from 

 Pericompsus only by the male having two joints of the anterior tarsi dilated, 

 by the anterior tibise being somewhat rounded at tip, and by the elytra having 

 a short scutellar stria. They differ among themselves by the comparative size 

 of the middle portion of the mentum, which in the species with impressed square 

 spots is longer and broader than in the others, and also in the comparatively 

 larger size of the first dilated joint of the anterior tarsi in the same species. 

 Nevertheless, taking into account the great variations in character, especially of 

 the mentum, in other groups, it seems to me more natural again to unite them 

 into one genus, to be called Bembidium. And with a view of shewing the re- 

 lations between the different groups, the following table may be made use of. 



BEMBIDIUM Latr. 



Legio Ima. Elytra humeris subangulatis, stria 8va a margineremota, inter- 

 stitio 3io punctigero. 



A. Mentum dente brevi bicuspi ; elytra striis abbreviatis. 



I. Elytra interstitiis seriatim parce punctatis, setiferis. {Ilydrmm Lee.) 

 II. Elytra glabra, interstitio 3io bipunctato. {Eudromus Kirby.) 



B. Mentum dente magno, integro : elytra striis integerrimis. 

 III. Elytra interstitio 3io bipunctato et foveis quadratis 



impresso. (^Bembidium Lee.) 



IV. Elytra interstitio 3io bipunctato, baud foveato. 



* Annales de la Soc. Entom. de France, 2nd Ser. 9, 462. 

 t Trans. Am. Phil. Soc. vol. x, STD. 



1857.] 



