62 PROCEEDINGS OF THE NATIONAL MUSEUM vor,. iii 



than in males of either 0. alluvius or 0. knulli. Clypeal disc and frons 

 almost flat and lacking both clypeal and frontal carinae, the latter 

 being poorly indicated behind eyes; surface between punctures finely 

 alutaceous. Margin of gena noticeably arcuate laterally, anteriorly 

 forming a distinct, obtuse indentation with the clypeal margin; gena 

 sharply, obtusely angulate posteriorly opposite the pronotal angles; 

 surface of gena slightly concave and with scattered coarse punctures. 



Pronotum moderately convex, margined anteriorly and laterally; 

 pronotal protuberance a conical median hump, barely projecting over 

 the posterior portion of the head. Surface distinctly alutaceous and 

 with punctures of two sizes: larger punctures annular with margins 

 sharply defined, centrally with an erect reddish-yellow seta, the large 

 punctures usually separated by about two diameters; small sec- 

 ondary punctures hah the diameter of large punctures and nearly as 

 numerous, scattered among large punctures; small punctures with 

 sharply delimited margins and lacking central seta. Elytra with 

 feebly shining, vaguely punctate striae ; mtervals opaquely alutaceous 

 with irregular double rows of small shining tubercles; the base of 

 each tubercle with a fine reddish-yellow seta. 



Pygidium \vith very shallow, coarse, setigerous punctures scattered 

 evenly over surface; en the pygidium except extreme apex opaquely 

 alutaceous; evenly, only slightly convex. All ventral surfaces black 

 except for antennae, tibiae, and tarsi which are tinged with brown. 

 Ventral surfaces of metasternum coarsely punctured, more so laterally; 

 lateral surface between punctures finely alutaceous. Metasternum 

 near midline with a few large punctures and numerous fine ones 

 (metasternum distinctly more punctate near midline than in Texas 

 specimens of knulli); midline posteriorly vaguely mdented. Ventral 

 segments of abdomen and legs not differing noticeably from those 

 described for holotype of 0. alluvius, except that the punctures on the 

 femora are larger and more numerous than is usual for alluvius. 



Male minor. — ^Paratype, length 4.3 mm., width 2.6 mm. Differing 

 from the holotype male major in the following respects: Clypeus 

 much less sharply reflexed, distinctly emargmate; surface rather 

 evenly, coarsely, rugosely punctate. Clypeal carina lacking; frontal 

 carina low but distinct, slightly indented medially. Gena not greatly 

 produced but stUl angulate near pronotal angle. Pronotum less con- 

 vex; pronotal protuberance obsolete, very faintly indicated by a 

 slightly less alutaceous area; pronotal punctures similar but shallower 

 and more widely spaced than in holotype (or other male majors). 

 Elytra and pygidium similar to male majors except that pygidium is 

 alutaceous to apex. Ventral surfaces brownish black, slightly more 

 heavily punctate. Forelegs greatly shortened, the forefemur barely 

 extending to the lateral pronotal margin and the foretibia propor- 



