156 Trans. Acad. Sci. of St. Louis. 
prothorax small, strongly obtrapezoidal with the sides straight, much 
wider than long and distinctly narrower than the head, the angles 
distinct and only moderately rounded; elytra quadrate, subequal 
in width to the head, the sides parallel] and feebly arcuate. Length 
7.5 mm.; width 1.85 mm. Arizona (Williams), — Mr. Wickham. 
arizonense D. sp. 
The secondary male sexual characters are very simple, 
consisting of a large and broadly rounded shallow sinus 
at the tip of the sixth ventral segment. The species seems 
to be rather rare and I have only seen two specimens thus 
far. 
Polymedon 2. gen. 
This genus is also represented within our limits by a single 
species, which is very abundant, but, rather singularly, the 
only sex known to me is the female and I have searched in 
vain for the male through the numerous specimens in my 
cabinet. The male sexual characters are, however, probably 
simple. I have not been able to indentify Polymedon with 
any of the many Mexican genera made known by Dr. Sharp, 
and it is probably a local type, confined to the arid parts of 
the Sonoran regions. The type species may be described as 
follows :— | : 
Body moderately stout and convex, parallel, dark red-brown throughout, 
the elytra rather more rufous; integuments densely dull because of the 
rather coarse and mutually subcontiguous punctures, the elytra feebly 
shining and less densely punctate, the abdomen very minutely punctu- 
late and also slightly shining; head moderately large but not quite as 
wide as the elytra, parallel and feebly arcuate at the sides, the basal 
angles broadly rounded; prothorax much narrower than the head and 
almost as long as wide, feebly obtrapezoidal, the sides straight, the 
angles obtusely rounded; elytra subquadrate, scarcely as long as wide, 
about a fourth wider than the prothorax and almost two-fifths longer, 
the sides parallel, feebly arcuate posteriorly. Length 4.5 mm.; width 
0.9 MM. ATIZONA..coesseee cee o teeecces eee eeeeesces -tabacinum Csy. 
The specimens at hand are from various parts of Arizona, 
and, in some, the head is relatively a little smaller, with the 
neck somewhat wider, but I can discover no other specific 
differences. 
