Genera of the Cossonidce. 525 
are also more fusiform, or less parallel, insects than the 
PentartJira ; their protliorax is more rounded and convex ; 
their elytra are less straightened, and more lightly sculp- 
tured ; their rostrum is a little longer and less robust ; 
and their antennas (which are implanted a trifle nearer to 
the apex of the latter) have their scape slenderer and 
more curved. There is also a peculiarity about their 
undersides (which is likewise the case in most of the 
Microxylobii and Acanthomeri, as well as in Lampro- 
chrus, and in many of the true Cossonides), — the first 
abdominal segment and the (very short) metasternnxn being 
deeply impressed (at any rate in the two Atlantic-island 
species) down the central region, causing them to be 
hollowed-out, or concave. Two out of the three Amau- 
rorrliini with which I am acquainted (namely the A. 
Monizianus and Bewickianus) are found in the Madeiran 
archipelago, and one of them likewise at the Canaries, 
whilst the other occurs in the south of Europe ; but the 
slight singularity in their modes of life, which apjDcar to 
be much the same as those of Pentarthrum (as well as of 
Hexarthrum, of the true Cossoiiides), renders it probable 
that they will be found eventually to possess a more ex- 
tended range. 
28. PsEUDOMESOXENUS {jLOv. gen.). — The little insect 
(hitherto unique) for the reception of which the present 
genus is established was taken in the island of St. Helena 
by Mr. Melliss; and it was recorded by myself, three 
years ago, as a blind, aberrant Pentarthrum, under the 
name of P. suhccBcum.* It is evident however that it has 
a far closer affinity with Amaurorrhinus , — with Avhich 
indeed its obsolete eyes and scutellum, and its convex, 
largely-developed prothorax, would tend to affiliate it. 
Still, an accurate examination of its structural details has 
convinced me that it cannot be ti'eated as even an Amau- 
rorrhinus ; for not only is its metasternum very appreci- 
ably more elongated, and its rostrum thicker and sub- 
trianrjular, but its elytra likewise are narrower and more 
parallel and cylindrical, and its limbs are shorter and less 
thickened, — the feet especially being slenderer and filiform, 
with their third joint almost unexpanded and simple. 
The underside moreover is convex, and has no trace of 
the concavity which gives so remarkable an appearance to 
* Vide ' Ann. Nat. Hist.' iv. 410 (1869). 
2 P 2 
