448 TERTIARY INSECTS OF NORTH AMERICA. 



8. NECROCYDNUS REVECTUS. 



A very broad, stout, and rounded species. Head rather small, well 

 rounded, at least half as broad again as long and scarcely a fourth as wide 

 as the thorax ; the antenna? about as long as the thorax. Thorax about 

 twice as broad as the median length, with strongly arcuate, somewhat 

 oblique sides, which curve rapidly on the anterior half to the ends of the 

 apical emargination, which is hardly one-third as long as the basal margin, 

 moderately shallow and very regular; surface even, finely, uniformly, and 

 densely punctate, as is every coriaceous part of the body. Scutellum nearly 

 half as broad as the thorax, considerably broader than long, the scarcely less 

 than rectangular apex not extending half-way to the apex of the abdomen. 

 Hemelytra reaching as far as the tip of the abdomen, the membrane small. 

 Abdomen very broadly rounded posteriorly, somewhat shorter than broad. 



Length, 4.5 ; breadth, 3.2 mm . 



Florissant. Two specimens, Nos. 1581, 10844. 



4. THLIBOMENUS gen. nov. 



This genus is even more closely allied to Necrocydnus than the latter 

 to Procydnus, and differs from it principally in the still greater prominence 

 of the head, which is out of direct relation to the general anterior curve of 

 the body, the anterior emargination of tlie thorax being slight or even 

 absent. The head is nearly circular, generally a little, but only a little, 

 broader than long, the eyes central, moderate in size and prominence, glob 

 ular, the ocelli well behind them, pretty large, and as near each other as 

 the neighboring eye. Thorax about twice as broad as long, subquadrate 

 the sides very variable, but the tapering usually confined to the anterior 

 half, or very much stronger here than posteriorly, the front margin but 

 slightly emarginate, usually also very broadly rounded or subtruncate, with 

 a strongly arcuate anterior sulcation terminating next the sides of the 

 head ; the basal margin truncate. Scutellum precisely as in Necrocydnus. 



The species are pretty numerous, but are known only by one or two 

 examples each. They are mostly of the smallest size, and all come from 

 Florissant. 



TaliJe of tlir species of ThJibomeims. 



Outer auterior angles of the thorax prominent, the length of the apical margin of the thorax not 



greatly less than that of the basal. 

 Thorax Cully twice as broad as long .............. ................................... 1. 7'. jieln .-. 



Thorax scarcely twice as broad as long .............................................. 2. T. pari-tis. 



