NORTH OF MEXICO. 



261 



TRIMYTIS, Leo. 



Trimytis, Lee, Ami. Lye. V, 141. 



With this genus commences a series of an oval, rather robust form. In them the 

 thorax is as wide at base as the base of the elytra. The intercoxal process of the abdo- 

 men is triangular and acute. The form of front in Trimytis is nearly that seen in the 

 preceding genus. The middle lobe is broader with sides less convergent, and truncate, 

 the lateral lobes are small, rounded and separated from tin; middle lobe anteriorly by a 

 fissure or incisure, as in Triphalus. The eyes have slight superciliary ridges, more de- 

 veloped in front of the eyes than above them. 



T. pruinosa, Lee., Aim. Lye. V, 141. Form elongate oval, convex, glossy black. Head and thorax densely 

 but not very coarsely punctured. Thorax one-half broader than long, sides slightly rounded, gradually narrowing from 

 hind angles, which are rectangular, apex emarginate, base truncate, anterior angles prominent acute. Elytra oval 

 truncate at base, scarcely wider than the thorax at base, with eight discoidal and one marginal row of rather line 

 punctures becoming obsolete at the apex; the interstices have a, single row of very fine punctures. Thorax beneath 

 rather coarsely hut not densely punctured, abdomen finely and very distantly punctured. Length .35 Inch. 



Found at times rather abundantly under stones on the plains west of Missouri. When recent the individuals 

 have a pruinosc appearance, or as if covered with a fine dust-like, efflorescenoe. 



Length .20-24 inch. 



T. pulverea, n. sp. Pioeous, sub-Opaque, elongate, oval, moderately convex. Head finely silicate from the lon- 

 gitudinal confluence of punctures. Thorax one-half broader than long, convex, moderately, coarsely and densely 

 punctured, sides moderately rounded. Base faintly sinuous, angles rectangular. Anteriorly slightly emarginate; an- 

 terior angles not very prominent. Elytra, oval truncate at base, with eight discoidal rows of rather large punctures 

 and one marginal; interstices slightly convex with a faint series of punctures. Thorax beneath very coarsely and 

 densely punctured. Abdomen lews coarsely and not densely punctured. Length .20 Inch. 



This species differs considerably from the preceding, notably in the form of the thorax. 

 The thorax is rather narrower at base than at its middle, the sides are therefore more 

 rounded than in jprwinosa and the anterior angles are much less prominent. 



As compared with pruinosa, this species has more elongate and less convex elytra. 

 The rows of punctures are better defined and the punctures more closely placed, 

 so that the elytra are almost striate. When recent, this species is covered with a fine 

 dust, as in pruinosa. I found but few specimens of this species at ('amp Grant, Arizona, 

 during the Winter, under stones, etc. 



T. ab nor m is, chestnut brown, sub-opaque; head rather densely and coarsely punctured; thorax broader than 

 long, narrower at base than the elytra; disc moderately convex, coarsely and moderately densely punctured, especially 

 toward the margins; apex feebly emarginate, base slightly sinuate, sides rounded in front, gradually narrowed to the 

 hind angles, which are rectangular. Elytra elongate oval, subparallel in front, moderately convex with stria: of finely 

 muricate punctures, confused at base and less distinct at apex. Body beneath coarsely but not densely punctured; 

 abdomen paler, more shining, and scarcely at all punctured. 



Length .20 inch. 



This species differs not only from all its congeners, but from the group of genera, in 

 reproducing a form of thorax more nearly allied to Stibia; all the other species of the 



AMERI. PH1LOSO. SOC. — VOL. XIV. — 66 



