20 
generally tricostate. The elytra are generally trigonal, at times 
oblong, depressed or slightly convex, their surface sometimes 
even, but generally furnished with a ridge on each at the base, 
which often projects forwards, and in many species is prolong-ed 
posteriorly to the apex : the latter is generally briefly and ob- 
liquely truncated, but it is sometimes whole, and at other times 
largely truncated, with the external angles projecting into a 
tooth or spine. The pro- and mesosterna are moderately broad, 
but variable in this respect ; the former never very narrow, the 
latter not contracted between the haunches nor extremely short, 
but always of a quadrangular shape. Both are plane on their 
surface in some species, but they are more generally tumid or 
tuberculated, ridged on the sides, and projecting : in a number 
of cases the mesosternum is projecting, whilst the prosternum 
is simple ; in many species, however, both project and have their 
opposing faces steeply inclined. They vary greatly in species 
otherwise closely allied, although they are similarly constructed 
in all those species which approximate to Steirastoma. The tibise 
are, in one section of the genus, strongly dilated and compressed. 
The terminal ventral segment is sinuate-truncate in the 6 , and 
entire in the $ . 
The flattened shape of the muzzle distinguishes this genus 
from the preceding. There is no character to separate it from 
Dryoctenes, Serv. The shape of the sterna distinguishes it from 
Polyrhaphis. From Steirastoma it differs at once in the simple, 
conical, lateral thoracic tubercles ; and from Alphus by the pyri- 
form basal joint of the antennse. I have incorporated with it the 
genus Pteridotelus, White, — with some hesitation, however, as I 
think Pteridotelus might probably form a natural group if the 
generic definition were modified so as to include all those spe- 
cies which have the terminal joints of the antennse shortened 
and thickened in any degree, or thickened and ciliated in 
the d. The species on which it is founded [Pteridotelus 
laticornis) cannot be generically separated from A. pupillatuSy 
Chevrolat, which, again, is closely allied to A. spectahilisy n. sp., 
and A. pilicornisy Chevr.*, all four most diversified in ornamenta- 
tion of the antennse, but agreeing in the thickening in some 
way or other of the terminal joints. These species have in 
common also rounded anterior acetabula, slender fore tibise, and 
steeply inclined sterna. As a genus, however, it would not be 
sharply limited from Acanthoderes : other species have the ter- 
minal antennal joints somewhat shortened and ciliated, without 
* To these may probably be added A. antennatus of Guerin-Meneville 
(Ins. Recueillis par Osculati, Verb, des Z. B. Verein in Wien, 1855, p. 599). 
A. pupillatus is from Venezuela, and A. pilicornis from Mexico ; both are 
imdescribed. A. spectabilis belongs to the Amazonian fauna. 
