NORTH AMERICAN COLEOPTERA. 
279 
Head. — The front may be flat, moderately convex, or very con- 
vex. In the latter case the month seems more retracted and inferior, 
as will be observed in the sjiecies from jmlchelhis to muticus, but va- 
rying in degree, so that this character fails to be useful foi’ generic 
separation. In nearly all the species the head has a median im- 
])ressed line beginning at the occiput, but this varies both in extent 
and depth, forming in several sj)ecies a deep frontal depression or 
even concavity. The clypeus varies somewhat in form, but not to 
the extent observed in Chrysobothris, so that no use has been made 
of it in the table. Sexually the head varies in sculpture and coloi', 
as will be found recorded, but the differences between the sexes are 
not by any means as well marked as in Chrysobothris, or in the more 
closely allied Anthaxia. Other characters of more resti-icted oc- 
currence will be found under the species in which they occur. 
Prothorax. — The usual thoracic characters based on color, sculp- 
ture and the depressions require no S{)ecial comment. The carina of 
the hind angles has nearly always been mentioned from the earliest 
descriptions, and its presence or absence regarded as an infallible 
sign of specific distinction. It remains now to be recorded that in a 
number of species the presence or absence of the carina is often 
purely sexual, the male being without it. This is well shown in a 
series of acutipennis. In all cases the presence or absence of carina 
must not be assumed to be of specific value, except when accompanied 
by other characters. 
The lateral marginal edge of the thorax assumes two forms when 
viewed from the side, the sinuate and straight. The former is the 
more usual, and is well illustrated by macer (PI. viii, fig. 9), while 
the straight form is mostly seen in the cylindrical species, such as 
lacndris, etc. (PI. viii, fig. 10). 
Prosternum. — The prosternal lobe varies in length and form, 
sometimes almost entirely concealing the mouth. Its anterior margin 
may be broadly rounded as in cavatm (in which the mouth is nearly 
concealed), truncate as in bllineatus, or emarginate, as is the more 
usual occurrence. Various forms of emargination will be observed, 
the most irregular being in difficilis, in which the notch is small, and 
on each side there is a sinuation. 
The tip or apex of prosternum is subject to great modification. In 
many species the tip is continuous with the intercoxal portion and 
enters the metasternum by a triangular notch, while in others the 
tip is abruptly bent upwards and enters the metasternum concealed. 
