408 Records of the Indian Museum. [Worn at 
was found to differ from the other species of Dovcus in our collection 
in the opposite direction. Further investigation then showed 
that the prosternal process of both sexes of the latter species was 
elevated as in Hentisodorcus, not flattened asin Dorcus ; and that 
the anterior plates of the head of the male of the former species 
resembled those of Eurytrachelus, not Hemitsodorcus. 
Thomson ! defines these genera—including as a distinct genus 
Platyprosopus, which Van Roon unites in his catalogue with 
Eurytrachelus—by means of the structure of the mandibles and 
anterior plates of the head of the male, and the structure of the 
prosternum. Hemisodorcus is said to differ from the other three 
genera in having elongate mandibles, and this character appears 
to have been regarded by subsequent authors as being in itself~ 
diagnostic of the genus. But it is not correlated with the other 
so-called generic characters, and a consideration of the female 
points to the conclusion that it is of less importance than them. 
The material in our collection does not enable me to deter- 
.mine whether these other characters are always sharply distinctive, 
or sometimes grade into one another, but it proves clearly that 
the extent of their development shows a considerable degree of 
variation in different species. Thus the posterior end of the pro- 
sternal process, though it is always much higher than the mesoster- 
num and more or less abruptly truncate in Hemisodorcus and 
Eurytrachelus, and is depressed in the most typical species of Dorcus 
and Platyprosopus, is sometimes, in the genus Dorcus at least, 
distinctly convex immediately in front of a narrow depressed 
posterior margin. 
In the table for the determination of these genera given below, 
I have found it convenient to attach primary importance to the 
structure of the prosternum, because this applies to both sexes.’ 
But when dealing with males only it is often easier to consider 
first the character of the anterior plates of the head. 
These plates, the clypeus and labrum, appear to be more or 
less fused in most, if not all, Lucanidae; and the plate thus 
formed—which may be termed the clypeolabrum—is often itself 
indistinguishably fused with the frons. Among the species before 
me the outlines of these plates are best seen in Lucanus cantori. 
In the female of this species the clypeus is less coarsely punctured 
than the frons, and is bounded behind by a tolerably distinct 
suture; it is very narrow and is keeled in front, overhanging by 
almost its whole width the larger, still more sparsely punctured, 
and much more hairy labrum.® 
In the male the ridge between the clypeus and the labrum is 
8 In the females of most species the labrum is much smaller and the clypeus 
somewhat larger ; consequently the labrum is much obscured. 
