628 Mr. D. Sharp and Mr. F. Muir on the Comparative 
these are three, viz. Passalidae, Lucanidae, Scarabaeidae. 
We will return to this point after touching on the 
peculiarities of the group. 
The first of these is that in the enormous majority of 
the forms there is a great reduction of the scleritic parts 
of the median lobe. If the characters of a Lucanid and 
a Scarabaeid be examined, it would at first be supposed 
that but little real affinity exists between the two. On 
the other hand, if Zrox (usually placed in Scarabaeidae) 
be added to the compared material, the difficulty becomes 
that of separating the two divisions, for 7’rox agrees better 
with Lucanidae than it does with Scarabaeidae. T'row is 
not only very important in this respect, but also because 
it throws some light on the very peculiar male structures 
of the Passalidae. 
The Scarabaeidae, while exhibiting a reduction of the 
scleritic parts of the median lobe, display an enormous 
development of the basal-piece, which forms the “tambour” 
(Straus-Durckheim) of the organ. This tambour usually 
shows a constriction which might at first sight be supposed 
to separate it into two parts, in which case the proximal 
part only would be taken as the basal-piece, and the 
distal portion might be supposed to be part of the 
median lobe. This, however, is a most superficial obser- 
vation; the constriction in question merely marks the 
attachment of the connecting membrane, the two portions of 
the tambour being one enormous basal-piece. The lateral 
lobes are most remarkable and are very diverse. They 
form what is usually, in this division, called the forceps. 
In some cases they are separate, not amalgamated, at 
their bases (Spilota, etc.); in another condition they are 
amalgamated on the dorsal aspect, forming an undivided 
piece (Pelidnota); while a third condition exists in 
Lomaptera (Cetoniinae), where the amalgamation of the 
lobes occurs on the ventral aspect. In Jschiopsopha by 
a modification of this they form a complete scleritic ring, 
as they do in Xylotrupes. The ventral surface of the basal- 
piece is usually membranous for a large area, but in some 
forms there is a chitinisation of this surface, to which we 
have applied a special name, the ventral-piece (fig. 19, 
vp). In some cases this ventral-piece becomes quite 
chitinously continuous with the lateral lobes (Xylotrupes 
e.g.), forming thus a very large irregulariy shaped 
sclerite. 
