Casey — A Revision of the American Paederini. 43 
Hesperobium Csy. 
The dentition of the mandibles will at once distinguish this 
genus from Gastrolobium, there being but two large elongate 
sharply pointed and much less unequal teeth, instead of the 
three teeth of the latter genus. The two teeth of the right 
mandible are clearly and evenly outlined throughout, but the 
lower tooth of the left mandible has a small shallow notch 
and vestigial tooth-like inequality of the edge far down on its 
lower side. The species, which are less numerous than those 
of Gastrolobium, differ considerably from the latter in facies, 
and, except in a few aberrant forms, in their sombre black or 
piceous coloration, longer basal joint of the antennae and 
type of male sexual modification, no trace of the folds, foveae 
or lobe of the second and third ventrals ever being observable. 
They appear also to be exclusively confined to temperate and 
boreal North America, not extending below the Mexican 
boundary and inhabit the entire country from the Atlantic to 
the Pacific, being the only genus of Cryptobia, except 
Ababacius, forming part of the true Pacific coast fauna. It is 
therefore the ancestral stem-forms of this genus, in all prob- 
ability, rather than the preceding that, migrating in remote 
times to Asia by way of Alaska, have gradually become the 
present Monocrypta, Spirosoma, Homoeotarsus and Crypto- 
bium of Asia and Europe. The species are tolerably homo- 
geneous but sellatum, perfectly normal otherwise, differs 
greatly in its pale elytra, maculate with black, and cribratum 
and rubripenne in some features of form and coloration, as 
well as the pale, very coarsely and sparsely sculptured elytra, 
call to mind the remarkable type of Lissobiops to be described 
below. The various species may be distinguished by the char- 
acters given in the following table : — 
Basal angles of the head more or less evident, the head more oblong; elytral 
punctures never very coarse, always close-set and never with more than 
a trace of serial arrangement at any part. ....0 ccc ceccceccsecececccs 2 
Basal angles of the head obsolete, the sides converging from the eyes to the 
neck and almost evenly arcuate; neck not more than three-fifths as wide 
as the head; elytral punctures extremely coarse, sparse and more or less 
distinctly serial in arrangement; surface polished throughout........ 13 
