42 Mr. F. P. Pascoe on some new or little-known 
subtriangular, gradually enlarging to the ninth, which, with the tenth 
and eleventh, are of equal thickness, the latter a little pointed at 
the apex; eyes prominent; mentum transverse, narrowed in front, 
its anterior angles produced; labium slightly emarginate ; maxillary 
lobes narrow, nearly equal in size, fringed with long hairs, the inner 
lobe with a strong hook at its external angle; palpi rather short, 
the terminal joint of the maxillary subcylindric, of the labial ovate ; 
mandibles bifid at the apex, with a slender tooth internally ; prothorax 
twice as long as the head, sparingly punctured, a small process at the 
anterior angle, posteriorly a little contracted, and at the base a curved 
impressed line ; scutellum broadly triangular, the sides rounded ; elytra 
about twice as long as the prothorax, punctate-striate, slightly concave 
between the suture and the external border, where they bend down 
almost at a right angle; cox not approximate; femora long, robust; 
tibiz short, slightly curved, subtrigonate, the posterior near the ex- 
tremity finely toothed at its inner edge; tarsi very short, the three 
basal joints dilated, the fourth minute, the claw-joint small, not longer 
than either of the three basal; body beneath dark brown, finely punc- 
tured. Length 3 lines. 
The insect is much narrower than I have represented in the 
figure. 
Acutnosvs [Tenebrionids ]. 
Caput exsertum, clypeo producto. Antenne subclavatee, articulis 5-7 
ultimis perfoliatis, transversis. Mazille lobo interiore hamato. Tibie 
antice trigonate, extrorsum dentate. Corpus subcylindricum. 
This genus differs in a few points only from Antimachus, some 
species of which it closely resembles, except that it is more cylin- 
drical, but from which it will be at once distinguished by the 
strongly serrated external margin of the fore-tibiee. There are also 
remarkable differences in the mentum and labium of the species 
described below, and in the same parts of a species of Antimachus 
(probably A. furcifer, Gistl) which I examined for the purpose of 
comparison. But two other species, which I refer also to Achthosus, 
appear to have the more or less subcordate mentum of Antimachus, 
and therefore I have not referred to this organ in the characters of the 
genus. So far as my limited experience goes, it appears to me that 
the parts of the mouth are subject to the same variations as other 
organs, and, except certain differences of plan, which, however, are 
rather characteristic of higher groups than genera, the variation in 
form or outline of these organs is generally only one of degree. I 
believe that they are supposed to be more constant in their cha- 
racters because they are seldom examined, and that one species is, 
as a matter of course, taken as the type of the rest. For this reason 
