NORTH AMERICAN COLEOPTERA. 
23 
coxal plates are obliterated externally, the posterior edge being con- 
fluent with the anterior. 
Occurs in Alaska. 
C. tliibius Horn. — Oblong, moderately convex, fuscous, feebly shining, 
sparsely pubescent, hind angles of thorax paler; antennae slender, scarcely ser- 
rate, fuscous, the three basal joints paler; head slightly flat, closely subasper- 
ately punctate; thorax a little wider than long, narrowed in front, sides parallel 
behind, arcuate anteriorly, the hind angles nearly rectangular, the cariua mod- 
erate in length, disc convex, the median line smoother, surface closely punctate 
and somewhat scabrous in front, gradually more smooth posteriorly ; elytra ob- 
long, sides parallel, arcuate at apical third, humeri obtuse, disc striate, a little 
less at the sides, strije relatively coarsely punctate, intervals flat, finely and 
moderately closely punctate; prosternum sparsely punctate, transversely im- 
pressed in front, the lobe short and obtuse, propleurfe finely and indistinctly 
punctate; metasternum more coarsely punctate; abdomen very finely and mod- 
erately closely punctate ; legs pale. Length 2 — 2.5 mm.; .08 — .10 inch. 
The under side of body is notably paler than the upper, especially 
on the sternal members and the epipleurte. The posterior coxal 
plates are obliterated externally. 
This species has the same general outline of body as in the Mel- 
sheimeri series, but is more convex. 
Occurs in Nebraska and Dakota (Ulke). 
Group PERPLEXUS. 
Prosternal sutures arcuate and rather strongly convergent poste- 
riorly. Maxillary palpi moderately prominent, the last joint elon- 
gate triangular. Elytra moderately deeply striate, ornate with yel- 
lowish spaces. Form rather slender, convex. Thorax simply 
punctate, not rugose, the median line not elevated nor smooth, with- 
out basal incisures. Legs slender, tibial spurs very small. 
Among the species with arcuate prosternal sutures, those of this 
group are known by the striate and ornate elytra, with comparatively 
smooth thorax. The only exotic species known to me as belonging 
here is quadrijnistulatus Fab. 
The species are separated as follows : 
Thorax distiuctly narrowed iu front, at base as wide, or wider than at middle. 
Antennfe and legs entirely piceous geiitilis. 
Thorax coarctate at base and apex nearly equally, widest at middle, hind angles 
slender, slightly divergent. Legs and three basal joints of the an- 
tennse yellowish testaceous. 
Elytral humeri obtuse, body with well developed wings, striae scarcely more 
punctate than the intervals ; each elytron with two yellow spaces, 
humeral and subapical sestivus. 
Elytral humeri rounded, body very feebly winged, striae more coarsely punc- 
tate than the intervals. 
Each elytron with two yellow spots; thorax wider than long. 
quadripustulatus. 
Each elytron with a humeral spot only ; thorax distinctly longer than 
wide perplexus. 
