NORTH AMERICAN COLEOPTERA. 
35 
apex, that of the female being much more acute and slightly ele- 
vated in an obtuse carina near the middle. The male has a few 
squamules on the anterior tarsi. Tibiie straight in both sexes. 
This species is the most depressed of any in our fauna, and has 
the thorax much more narrowed behind, resembling a diminutive 
Polpochile capitata. There is no depression of the lateral margin of 
the thorax, as is usual in our heretofore described species. 
Occurs from Fort Yuma eastward to Tucson, Ariz. (Wickham.) 
I>. crassicollis n. sp. — Form robust, convex, piceous, shining, without 
trace of metallic surface lustre; antennae, palpi, and usually the labrum, casta- 
ueous; head impunctate, frontal impressions very short; thorax quadrate, a 
little wider than long, slightly narrowed at base, widest one-third from apex 
sides regularly arcuate, margin not depressed, hind angles obtusely rounded, disc 
convex, median impression faint and short, basal impressions broad, but shallow 
and vague; surface smooth, with a few longitudinal wrinkles at base; elytra not 
wider than the thorax, sides feebly arcuate, disc convex, finely striate, stri® not 
punctate, intervals smooth, very feebly convex, the inner sides of 3-6-8 with 
the usual punctures fine and rather indistinct; body beneath slightly paler, 
shining, prosternum not margined at tip, but with two (usually) prominent bris- 
tles on each side; abdomen very sparsely punctate, coarser punctures on the 
intercoxal process. Length 12.5 mm. ; .50 inch. 
Although reasonably certain that both sexes are before me in the 
live specimens examined, no well marked sexual difierences have 
been observed. The last ventral segment bears two setie on each 
side. The middle tibise are not longer than the anterior, are broader 
toward the tip, slightly arcuate and beset on the outer side with short 
spinules. The posterior tibise are also very slightly arcuate. The 
anterior tarsi are not furnished with squamules. 
This species is evidently very closely allied to acmopoides Bates 
(Biol. Cent. Am. Col. i, p. 63), which is described as having the 
elytra cupreous and the sides of the thorax straight and not arcuately 
narrowing as in the present species. 
It is the most robust and convex species in our fauna, quite unlike 
our others, and resembling an Acinopus more nearly than Discoderus. 
Occurs in southern Arizona. 
AJV.4TRICHIS Lee. 
This genus has been divided by Chaudoir (Ann. Fr. 1882, p. 322) 
into Anatrichis and Oodiellus, the former represented by ouv nihuita, 
the latter (which Mr. Bates very properly considers a synonym of 
Oodinm Mots.) typified by mexicanus Chd. (1882) = piceus Mots. 
(1864). In the paper above cited Chaudoir describes three addi- 
