1914-] ^- H. GRAVEI.Y : An Account of the Oriental Passalidae. 185 



It is then found that in addition to the inner and outer tubercles visible from 

 above, there is a third pair which may be called the ventral tubercles ; that the two 

 members of each of the three pairs are normally connected by a more or less distinct 

 ridge ; and that similar ridges tend to connect the different pairs together at either 

 end (see text-fig. i, D and E). None of these tubercles seem to be developed in 

 the Aulacocyclinae ; but below the fold which forms the anterior margin of the head 

 there is a ridge which probably corresponds to the one between the ventral tubercles of 

 the remaining subfamilies. From a taxonomic point of view the most important of 

 the ridges found in the second section of the family is that between the inner 

 tubercles. Its absence in the Pleurariinae is one of the characters by which this 

 aberrant sub-family is distinguished from others; and the fact that it forms the 

 anterior margin of the head as seen from above is the principal character by which the 

 Leptaulacinae are distinguished. In most forms in which it is present other than 

 the Leptaulacinae, it is straight or slightly curved inwards towards the central tuber- 

 cle; but when it follows any different course this is usually found to be extremely 

 constant, and in the genus Macrolinus it seems to be a remarkably good character by 

 which to distinguish one species from another. The area enclosed by this ridge and the 

 two frontal ridges is termed the frontal area ; it is very variable in shape on account 

 of the variability of the frontal ridges. The other ridges are not sufficiently well 

 developed to be of use in the diagnosis either of groups or of species. 



The outer tubercles are usually of very great importance^, particularly in the case 

 of asymmetrical forms, though the characters they afford must always be used with 

 considerable caution on account of the frequency with which they are modified by 

 friction, sometimes in what appear in other respects to be remarkably fresh and 

 perfect specimens. 



In many species the outer tubercles, when viewed from the outer side, are found to 

 be horizontally grooved, and I am inclined to regard this groove as the dividing line 

 between the clypeus and frons (see text-figs, i D and E, and figs. 36a, 37a, 38(2, 39a, 40a 

 and 4irt). This groove is always situated below all that can be seen of the outer 

 tubercles from above, and in species in which these tubercles are forked or trunctate at 

 the end it always crosses the apex of the lower angle — a fact which often enables one to 

 distinguish fresh specimens of such species from worn ones of others in which these 

 tubercles are normally conical. From this it follows that the whole of these tubercles 

 as seen from above belongs in reality to what is here considered to be the frons instead 

 of to the clypeus. The course of the suture between the outer tubercles is very obscure. 

 If it is visible at all (of which I am doubtful) it must follow the ridge direct from one 

 of these tubercles to the other. But the pupae of Leptaulax dcntatus which I have 

 examined, suggest that the whole of the upper surface of the front of the head of that 

 species is frons, and that everything below the folded margin is clypeus — i.e. that 

 the junction of the two is along the ridge joining the outer tubercles together by 

 way of the inner tubercles, and not along the ridge joining them direct. 



The genus Gnaphnlocncniis affords the most important exception I know. 



