124 COLEOPTERA OF NORTH AMERICA. 



into groups and genera, the indications of Mr. Crotch and Dr. 

 Chapuis, except where they were in manifest conflict with our 

 judgment. The species live exclusively upon fungi. 



Tarsi distinctly .5-jointed. MaxilL-e without apical tooth. Dacnes. 

 Tarsi with fourth joint small, connate with the fifth ; 



MaxilL-e not toothed at tip. Tkitomata. 



Maxilhe with two apical spines. Ekotyli. 



txroup I. — Dacnes. 



A few species of very different sizes represent this group on 

 both sides of the continent. The genera may be distinguished 

 as follows : — 



Tarsi narrow ; 



Antennae with tenth and eleventh joint connate. Ploeosoma. 



Antennae distinctly 11-jointed. Dacne. 



Tarsi dilated, spongy beneath, fourth joint smaller. Megalodacne. 



Hypodacne Lee. is synonymous with the previously described 

 Atlantic island genus Ploeosoma Wall. The first genus has one 

 species in tiie Atlantic region, and in the Antilles, the second 

 on both slopes of the continent. The third is represented by two 

 species in the Atlantic region. 



Group II. — Tritomata. 



In the genera composing this group, the tarsi are pseudo- 

 tramerous, that is to say, the fourth joint is very small, and the 

 preceding ones dilated and covered beneath with .a brush-like 

 pubescence. The maxillae, as above mentioned, are not toothed, 

 and the last joint of the maxillary palpi are triangular and dilated. 

 The genera of this group have, perhaps, been unreasonably mul- 

 tiplied; but, as stated and defined by the limited representation 

 in our fauna, may be tabulated as follows: — 



Last joint of palpi widely securiform. 



Eyes coarsely granulate. Ischyrus. 



Last joint of palpi oval, or slightly triangular: eyes finely granvilate. 



Middle area of menlum large, transverse. Antennal clnb 4-jointed. 



Mycotretus. 



Middle area of mentum small, triangular. Tritoma. 



We have suppressed Cyrtotriplax Crotch, as not sufficiently 

 distinct from Tritoma Fahr. (nee Geoffr.), and Triplax as defined 



