290 G. n. HORN, M. D. 



allel, narrower than thorax, one third longer tlian wide, at base deeply einar- 

 ginate. angles very prominent anteriorly ; sides nearly straight, slightly sinuata 

 near tlie humeri ; surface feebly striate, strise punctured, intervals flat, biseri- 

 ately punetulate and each puncture with an erect hair. Body beneath very 

 sparsely punctured. Length .20 — .22 inch ; 4 — 4.5 mm. 

 Occurs in the Grulf States, usually with ants. 



RHYSSEMUS, Muls. 

 Three species are known to me in our fauna. The genus niay" be 

 easily known by the characters given in the table from all excepting 

 possibly Psammndius. In Rhi/s^emus, the hind tarsal joints are flat- 

 tened and subtriangular as in Psammodius. The latter has the mar- 

 gin of thorax fimbriate but with slender hairs, and in the present genus 

 they are clavate. The hind femora in Rhj/sseimis, are more slender 

 than those of the first pair, and the spurs slender and acute while the 

 reverse is the case in Ps<nnmodhis. In th 3 latter genus the transverse 

 elevations are smooth and the grooves punctured in Rhi/ssemiis, the 

 former are made of larger tubercles while sujaller ones fill the inter- 

 spaces. These characters will serve to distinguish the two genera 

 without recourse to that derived from the external maxillary Icbe 

 which although more to be depended on is difficult to observe with- 

 out dissection. 



Rh. scaber, Hald. Journ. Acad. 1848, p 107. — Black; subopaque. Head 

 coarsely verrucose, clypeus emargiuate and on each side obtusely rounded, be- 

 hind the emarginatiou depressed, margin of head rufous. Thorax moderately 

 convex, with four transverse elevated ridges interrupted at middle and. 

 smoother, intervals with rather fine granules, more opaque than the ridges. 

 Elytra oblong sides moderately rounded, striate, strise not punctured, intervals 

 •with an acute elevated ridge sub-serrate at apex and a line of elongated tuber- 

 cles. Body beneath shining, sparsely jiunetured, legs rufo-piceous. Length 

 .14 — .Ifi inch ; 3.5—4 mm. 



Occurs in wet places along the Atlantic region. 



Rh. californicus, n. sp.- — Black opaque. Head sjiarsely verrucose, clypeus 

 emarginate and on each side distinctly sub-angulate. Thorax one fourth longer 

 than wide and distinctly narrowed at base, sides (viewed laterally) nearly 

 straight, disc convex, and with four very indistinct transverse ridges interrupte<l 

 at middle, and a distinct impression at each anterior angle, surface with moder- 

 ately fine granules. Elytra oblong, subparallel, striate, strise punctured, inter- 

 vals flat distinctly biseriately tuberculate. Body beneath more shining sparsely 

 punctured. Legs rulo-piceous. Length .12 — .16 inch; 3 — 4 mm. 



Occurs in sandy places on the margins of streams near Visalia, Cal. 



Easily known from sr(djer, by the very indistinct thoracic elevations 

 by the elytral sculpture and the pure blackness and opacity of surface. 



Rh. riparius, n. sp. — Brown oi>aque. Head rather coarsely verrucose, vertex 

 with two short elevated lidges converging above without joining, clypeus emar- 



