1 8 MEMOIRS ON THE COLEOPTERA 



Group IV Icevigatum 

 Subgenus Hydrium Lee. 



The sole representative of this group is the large polished, steel- 

 blue species described by Say under the above name. It is pecu- 

 liar among all other species of the genus known to me in two par- 

 ticulars. First, the form of the mentum tooth, which is short, 

 broad and truly bidentate, the incisure between the lobes being 

 deep and angulate. In all the other instances of a bidentate tooth 

 which have been recorded, the apex is simply sinua to-truncate, 

 the sides of the truncature being slightly prominent. The second 

 special character of the group is the complete absence of the usual 

 dorsal setigerous punctures or foveae, two or three in number in 

 nearly all other species of the genus; here, the absence of these tac- 

 tile setae is compensated by numerous setigerous punctures along 

 all the intervals, widely spaced in one or two rather uneven series. 

 The head is small, as in the nitidum group. LeConte had rather 

 plausible grounds for considering lamgatum to be a distinct genus 

 of the Bembidiinse, and it is not at all certain that this view may 

 not be correct. 



Group V erasum 

 Subgenus Lionepha nov. 



The type species of this group, which is really rather closely allied 

 to the ustulatum group, was placed with nitidum by Hayward, but 

 does not belong there on account of the obtuse humeri and general 

 habitus, but is much more closely allied to iridescens and a number 

 of other species assigned to the planatum group by that author. 

 The species are very numerous and rather troublesome to the sys- 

 tematist, because of the slight amount of structural diversity. The 

 body is always at least moderately convex and polished in great 

 part, with impunctate or excessively minutely punctate, striae, 

 which are generally obsolete externally, or, if present, very much 

 finer there than toward the suture. The dorsal foveae, always two 

 in number, are partially on the third interval but closely adherent to 

 the third stria and confluent therewith; they are generally said to 

 be on the third stria and vary from small to notably large in size. 

 The mentum tooth is well developed, broadly triangular and never 

 truncate at tip so far as observed; it is diversified so slightly as to 



