of the Amazon Valley. 121 
long, its front oblique and bituberculated. Prosternum simply 
rounded. 
The narrowness of the head across the vertex, and the con- 
sequent approximation of the antenniferous tubercles, which at 
the same time are very prominent, amply distinguish this genus 
from Acanthoderes, as well as from the following, Alphus. It 
has, in common with Alphus, the comparative slenderness of the 
basal joint of the antennee ; but this is more pyriform and shorter 
in comparison with the third in Myoainus than in Alphus. 
The form of the thorax and the crested ridges of the elytra con- 
tribute to give the species a peculiar facies. The name was first 
given, in Dejean’s Catalogue, to an undescribed species; the 
genus has never been characterized; the species to which the 
generic name was applied I have seen in collections, and it 
appears different from the one I took; both belong, however, 
decidedly to the same genus. M. Thomson (Classif. des Céram- 
bycides, p. 337) unites the genus to Alphus. It is more nearly 
allied to Alphus than to any other genus; but I think the 
characters given above will show that it should be separated 
from it. 
Myoxinus pictus, Erichson. 
Acanthoderes pictus, Erichs. Conspect. Ins. Peruan. p. 144. 
I took this species at Kga and St. Paulo. It is sluggish in its 
motions, and is found on dead branches of trees, to the bark of 
which the insect is assimilated in colours. I have nothing to 
add to the excellent description given by Erichson in the place 
quoted. 
Genus ALpuvus, Thomson. 
Thomson, Classif. des Cérambye. p. 10. 
M. Thomson notices the shape of the basal joint of the an- 
tenne, but, I think, not with sufficient detail to show the differ- 
ence in that respect between this genus and its allies. In Alphus 
this jot is very gradually thickened, and is nearly equal in size 
to the third; therefore it is not pyriform in shape, as is the rule 
in the Acanthoderite. The genus differs from Myozxinus in the 
greater breadth of the head across the crown; the head, however, 
is much narrower than it is in Acanthoderes and the allied genera; 
the muzzle also is much more obtuse. The genus, in fact, forms 
a connecting link between the Acanthoderite and the Acantho- 
cinitee, the chief character of the latter group being the great 
length of the basal joint of the antenne, which exceeds that of 
the third. The other characters of Alphus which require men- 
tion are the sockets of the fore haunches, which in most of the 
species are angulated exteriorly ; the fore tarsi, which are not 
dilated in the male; and the mesosternum, which is much nar- 
