208 MEMOIRS ON THE COLEOPTERA 



extreme to the foveate form prevailing generally in the genus; 

 perhaps the two shallow impressions sometimes seen near the pro- 

 notal apex in nasutus may be an analogous modification. Neither 

 Burmeister nor Bates makes any allusion to the deep concavity 

 extending throughout the width of the head between the eyes in 

 nasutus. 



Oxygrylius n. gen. 



There are but few structural differences between this genus and 

 Ligyrus, but two of these seem to be rather important the single 

 acute denticle of the clypeal apex and the more or less reduced 

 posterior tooth of the mandibles. In general bodily habitus it is 

 a counterpart of Ligyrus and also resembles it in the well developed 

 stridulating area on the under surface of the elytra, but the thoracic 

 fovea is constantly larger, deeper and is always at least partially 

 rugose at the bottom. The genus is not of very wide distribution, 

 inhabiting the region from the lower Rio Grande valley to the tip 

 of Lower California, so far as now known, and there are a number 

 of species, which however, as in all the allied genera, bear a close 

 mutual resemblance, so that care is requisite in studying them 

 systematically. The three forms now at hand are the following: 



Posterior tooth of the mandibles evident, though much reduced in size, 



obtuse 2 



Posterior tooth obsolete 3 



2 Body stout, more pyriform-oval, very convex, polished, dark rufous in 

 color, not paler beneath ; head nearly black, very densely and strongly, 

 rather coarsely punctato-rugose, abruptly smooth at base, the 

 carina high, feebly sinuate medially and not attaining the sides; 

 clypeus extremely densely and more finely rugose and dull, trian- 

 gular, almost three times as wide as long; mentum flat, rather closely 

 punctate and setose, gradually pointed anteriorly, the point obtuse; 

 posterior mandibular tooth not half as high as the middle tooth, 

 rounded, the first and second very acute; prothorax two-thirds wider 

 than long, the sides almost evenly rounded, becoming very con- 

 vergent apically, parallel basally, the basal angles, from above, only 

 very narrowly rounded; fovea rather large, rounded, a third the total 

 length, deep, rugose, the tubercle prominent; punctures everywhere 

 fine and sparse; scutellum wider than long, ogival, very minutely, 

 remotely punctulate, with an irregular line of larger punctures 

 parallel to the edges; elytra large, a fifth longer than wide, parallel, 

 circularly rounded in apical two-fifths, a fourth wider than the 

 prothorax and two and one-half times as long, the punctures in 

 series nearly as in Ligyrus and small, confused and sparse postero- 



