2 MEMOIRS ON THE COLEOPTERA 



generally closely retracting their legs and feigning death when 

 disturbed like Anthrenus and other Dermestids, as well as Ccenocara 

 and some other Ptinids. They are essentially boreal in habitat, 

 though a few more minute forms, belonging almost exclusively to 

 the Limnichinse, extend the range of the family well into the tropics. 

 They are evidently more numerous and structurally more diver- 

 sified in North America than in the palsearctic provinces, the very 

 aberrant forms having unretractile legs apparently being altogether 

 wanting in the latter regions. As occurring north of the Mexican 

 boundary in North America, they may be resolved into four sub- 

 family groups by the following primary characters: 



Mentum very large, filling the entire buccal opening; legs closely re- 

 tractile; antennae sheltered in repose beneath the anterior legs as 

 in the Byrrhinae; clypeal suture obliterated completely. Palsearctic 

 and nearctic ................................... NOSODENDRIN.E 



Mentum small or moderate in size ............................... 2 



2 Legs closely retractile ........................................ 3 



Legs perfectly free; clypeal suture wholly obliterated ................ 4 



3 Antennae sheltered in repose beneath the anterior legs; clypeal suture 



obsolete. Palsearctic and nearctic ................... BYRRHIN/E 



Antennae in repose exposed along the sides of the front above the eyes 

 or sheltered between the eyes and anterior part of the pronotum, 

 rarely lodged partially in pronotal excavations; clypeal suture 

 generally distinct, rarely obsolete; mandibles concealed in repose; 

 body more or less minute in size, the crural excavations deep and 

 sharply defined; last two ventral sutures stronger than the first 

 two, arcuate. Palaearctic and nearctic to neotropical. 



4 Antennae in repose wholly exposed along the under surface, sometimes 

 very long and subfiliform; surface very convex and shining, the elytra 

 sometimes substriate. Nearctic .................. AMPHICYRTINJE 



Nosodendron is considered the type of a separate family in the 

 most recent European arrangement of the Coleoptera, but in its 

 anatomical characters it agrees so closely with the true Byrrhids, 

 that its very large mentum should seemingly be held to have much 

 the same relative weight as the large mentum of Tentyria and 

 allies has when compared with the smaller mentum of the majority 

 of the Tenebrionidse. It would be far more rational to consider 

 Amphicyrta as typifying a distinct family than it would to place 

 Nosodendron in this category, but the number of groups having full 

 family rank could easily be increased unduly. 



The prefixed asterisks in the various tables indicate exotic genera 

 introduced for comparison. 



