19 
and flattened : eyes wide apart. Antennae slightly hairy, never 
fringed beneath as in Oreodera ; the basal joint always pyriform 
clavate, smooth, considerably shorter than the third. Thorax 
with a simple large conical tubercle on each side, generally 
ending in a spine. Femora strongly clavate; tarsi moderate, 
claw-joint short; fore tarsi in the d broadly dilated and 
ciliated. 
The above are the only characters that I find tolerably con- 
stant in the thirty-eight species which I have examined. The 
forms are very variable in most of the parts of structure from 
which generic characters are derivable, and exemplify well the 
difficulties which the Longicorn family offers to the classifier. 
No definition has yet been given founded on a large number of 
species That of Leconte Attempt to classify, &c.,-’^ Journ. Ac. 
N. Sc. Philad. ii. n. s.) is probably the best; but, relating only 
to the two or three North American species, it is not applicable 
generally. The rounded outline of the anterior acetabula, which 
he gives as a character of the section to which Acanthoderes be- 
longs, is very variable. In A. varius, the European species 
which may be considered typical of the genus, they are angu- 
lated ; in other species the acetabular sutures are gaping along 
their whole length ; in a few, however, they are closed. Although 
they differ in species otherwise closely allied, yet they are more 
constantly closed in those which approach Bteirastoina. The 
head is generally plane in front, the muzzle prolonged consider- 
ably below the eyes, the lower lobe of the latter being very 
small ; in some few species, however, the eyes are rather more 
voluminous below the antennae, thus reducing the breadth of 
the forehead and the length of the muzzle. The palpi are always 
elongated, with the terminal joint obtusely pointed. The ligula 
has its sides dilated and rounded ; the lobes, however, are widely 
divergent in some species (A. thoracicus) , and nearly united to 
their tips in others {A. bivittd). The antennae are very variable 
in length, thickness, and shape of the joints, being in some 
species no longer than the body, in others twice the length : the 
third joint is generally very long, and the fourth considerably 
longer than any of the following ; sometimes the two are as long 
as the remaining taken together; both are generally filiform, 
with a longitudinal furrow above, but they are occasionally di- 
lated and produced beneath at their apices, and in a few aber- 
rant species furnished with tufts of hairs : the terminal joints 
are generally filiform, sometimes short, thickened, and ciliated- 
in the 6 ) and sometimes dilated and serriform in both sexes. 
The thorax has the lateral tubercles, in rare instances, very 
obtuse; the dorsal surface is uneven, sometimes tuberculated, 
occasionally furnished with three very prominent tubercles, but 
n 2 
