[75] NORTH AMERICAN COLEOPTERA. 231 



the sides, triemarginaie, the notches being similar in shape, 

 deep, the middle about twice as large as the lateral; later- 

 ally the apex is broadly sinuate, thus giving four small, 

 acute, prominent denticles. In Medou, as represented by 

 M.fusculus Mann., the labrum is much larger, nearly flat, 

 broadly explanate at the sides, not at all sinuate laterally at 

 the apex, so that it is at most bidentate. 



In comparing the European Medon. as for instance brun- 

 neus Er., with many of the American genera, there is one 

 feature relating to the metasternum which appears to have 

 been generally overlooked, and which is indicated on the 

 upper surface by the length of the elytra. The metaster- 

 num in the European genus is remarkably short, strongly 

 convex, and much shorter than the intermediate coxse. This 

 appears to be a rather important character in the present 

 comparison, and distinguishes Caloderma at once, for in this 

 genus the metasternum is unusually well developed, and is 

 more than one-half longer than the coxa3, which in turn are 

 relatively distinctly smaller than in Medon. 



The species having a rugulose pronotum are the most 

 highly developed forms of the genus, and should be consid- 

 ered typical, although much less numerous in species than 

 the form with punctate pronotum. 



Oligopterus Cas. — Allied to Medon in prosternal and 

 metasternal structure. It differs from Medon in the struc- 

 ture of the labrum, which is here distinctly 4-dentate, and 

 from the more typical forms of that genus in the very 

 widely distant gular sutures, rapidly divergent toward base, 

 in this respect being more closely allied to Pseudomedon 

 Rey. It differs from Caloderma in its very short metaster- 

 num. 



Medon Steph. — This genus as represented in our fauna 

 will consist for the present of the two groups of species 

 previously placed by me in Lithocharis. There is another 

 group of nondescript species, occurring in the Southern 



