332 COLEOPTERA OF NORTH AMERICA. 



elytra without humeral angles ; palpi slender, last joint obtusely 

 pointed. 



Additional characters are: eyes rather finely granulated, small, 

 deeply emarginate ; front coxal cavities rounded, closed behind ; 

 middle coxal cavities angulated externally but closed; ungues 

 divaricate, last tarsal joint less elongated than in Dorcadiini. 

 Intercoxal process of 1st ventral segment wide. 



Mr. James Thomson has established Omoscylon on M. sub^ 

 rugosum Bland, a species of Lower California in which the pro- 

 thorax has no lateral spine. The distinction is illusive, as all 

 gradations in the degree of development of the spine are seen, 

 from M. armatum where it is large and acute to M. annulatum 

 Say, where it is obtuse, and finally to M. appressum Lee., and 

 subrugosum, where it is wanting. 



Tribe III.* TWIt IITIIYSOrUIAI. 



I have established this tribe on the very anomalous Michthy- 

 soma heterodoxum Lee., of which I found a single specimen in 

 the mountain region of Georgia. The head is rather large, the 

 front short, scarcely vertical, the support of labrum visible, cori- 

 aceous, labrum small, rounded in front. Palpi very unequal, 

 with the last joint securiform. Antenna slender, as long as the 

 body, scape rather stout, as long as the 3d joint, rounded at tip, 

 without cicatrix ; 3d joint not longer than 4th ; eyes small 

 elongate, coarsely granulated, lower lobe narrow. Prothorax as 

 wide as the head, with an acute lateral spine, rather in front of 

 the middle. Elytra elongate not wider than prothorax. Inter- 

 coxal process of first ventral segment acute. 



Front coxal cavities angulated, closed behind ; middle ones 

 angulated, closed externally; thighs strongly clavate, front tibi 

 curved inwards and feebly sulcate, middle ones absolutely without 

 tubercle, sinus, or tuft of hair on the outer margin ; tarsi less 

 dilated than usual, 1st joint of hind pair equal to two following 

 united; last joint moderate, claws divaricate. 



The form of the palpi seems to show an affinity with the 

 African genus Phantasis, but the body is much more elongate, 

 and the other characters do not agree. The head and prothorax 

 are densely punctured and opaque, the elytra more shining, less 

 densely punctured, with hairs proceeding from the punctures. 



