252 RHYNCHOPHORA. 
and other Corthylid genera; and these questions form the subject of a valuable 
critical paper by Eichhoff *, who correctly identified the type of the genus, Bostrichus 
compressicornis, as I have satisfied myself by an examination of Erichson’s actual type- 
specimen. He did not, however, see, and could only deal conjecturally with, those 
described by Ferrari. None of the latter’s species of Corthylus, sensu lato, belong 
to the genus, except his Pseudocorthylus, but of these one, P. glabratus, Ferr., belongs 
to Pterocyclon. Leconte correctly identified the genus, although he made an error in 
supposing O. punctatissimus to be its type (cf. Trans. Am. Ent. Soc. 1868, p. 144). 
The confusion which has surrounded this distinct genus has been largely due to 
ignorance of the sexual characters. The previous application of these was reversed by 
Hopkins (Canad. Ent. 1894, p. 277) for two North-American species, and his deter- 
minations by dissection clearly hold good for all. Eichhoff seems never to have seen 
a male of any species. The body in Corthylus is somewhat robust, never elongate. 
The forehead is subconvex in the male, excavate and often pilose in the female; the 
eyes are usually large, and extend below to the buccal region. ‘The antennee in both 
sexes have a single nodose joint representing the funiculus, and a flattened club, 
with two well-marked transverse, curved, or sinuate sutures on the outer face, often 
scarcely visible on the somewhat concave inner face, and sometimes with traces of a 
third suture near the apex of the outer face. In the male the scape is slender and 
the club small, nearly symmetrical oval or obovate, and without fringes. In the 
female the scape is enlarged into an oblong or subtrigonate plate; the club is very 
large, concave on its inner face, which is sometimes furnished with spongy patches, 
apparently sensory, and differing in situation in different species, and is of irregular 
shape, impossible to define with any precision, usually rounded triangular or sub- 
reniform, being produced on the lower side of the axial line, the upper and apical 
borders being either conjointly rounded or else separated by a rounded angle, the 
lower border being sinuate or angulate near its base. In tne females of most species 
the club is furnished with a fringe or flagellum of long cirri, arising from the upper 
limb of the inner surface and often matted together so as to simulate a spine. 
This flagellum is usually folded round the apical border of the club, which serves as 
a convenient index to its length. In those which have the flagellum absent or 
ill-developed, the club is smaller and not transverse. The hind angles, and usually 
the base, of the prothorax are bordered, the border in the males being continued 
forward along the sides; the apex in the males is usually furnished with two 
small prominent tubercles; the prosternum is excised in front up to the anterior 
cox. The elytral declivity is convex or retuse, and never produced, emarginate or 
divaricate at the suture. The femora are not robust; the tibiae are slender, 
scarcely widened apically, and armed with two or three teeth at the upper apical 
angle. ‘The tarsi are rather short. 
The previously-described species amount to twelve, of which three are from the 
