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 1.35 mm. Arizona (Williams), — Mr. Wickham. 



arizonense n. 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 n. 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 Polymedo7i 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 . Arizona tabaciunm 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. 



