120 Memoirs of the Indian Museum. . [Vol. VII, 



additional records contained in the present paper ; and in the case of other genera no 

 compilation is possible without a much more detailed revision of synonymy than I am at 

 present able to achieve. But the general distribution of the family requires some further 

 consideration in the light of certain facts set forth in the present paper. 



It will be convenient to deal with the Indo- Australian area first. 



This area is inhabited by three subfamilies of Passalidae, namely the Aulacocyclinae;,. 

 Macrolininae and Leptaulacinae. 



The Aulacocyclinae, though not a very large subfamily, appears to be a somewhat 

 highly specialized one. In none of its species are there frontal and parietal ridges or inner 

 and outer tubercles, such as are found in the more primitive species of all other subfamilies '■>- 

 and in the three largest genera, Comacwpes, Taeniocerus and Aulacocyclus the basal piece 

 and lateral lobes of the male genital tube form one piece, either by consolidation or by the 

 suppression of the basal-piece, instead of being separate as in other subfamilies (see Sharp 

 and Muir, 191 2, p. 580 ; also above, p. 5), while the middle lower tooth on each mandible 

 is immovable. In all other Passalidae, even in such primitive forms as Oileoides 

 subrecticornis, this tooth is jointed. Jointing does not occur, so far as I know, in any 

 beetles other than Passalids, and is clearly an indication of specialization ; but its absence 

 in Comacwpes, Taeniocerus and Aulacocyclus is probably secondary and not primitive, 

 especially as it is correlated with specialization of the male genital tube. In the two 

 remaining genera, Ceracupes and Cylindrocaulus , the structure, both of the tooth in question 

 and of the male genital tube, resemble those found in other subfamilies. 



The largest genus, Aulacocyclus, is centred in the Australian Region, but extends into 

 the Sunda Islands and Indian Peninsula. This discontinuous distribution suggests that 

 ground is being lost in the Oriental Region, where the smaller genera Comacupes and 

 Taeniocerus predominate. These genera are confined to the Oriental Region, except for a 

 single species of Comacupes (C. foveicollis) which has established itself in Celebes. Only 

 one species, Taeniocerus bicuspis, is found north of the Malay Peninsula ; this extends 

 northwards to the Himalayas. 



The genera Ceracupes and Cylindrocaulus, in which the male genital tube and middle 

 lower tooth resemble those of other subfamilies, only occur towards and beyond the 

 northern confines of the Oriental Region. With these presumably primitive characters 

 they combine cephalic excrescences which give them a most unusual appearance. Such 

 excrescences frequently indicate the senility of a group, and it seems probable that 

 Ceracupes and Cylindrocaulus are senile survivors of a transitional group through which 

 the more typical Aulacocyclinae of the present time have been derived. Ceracupes is less 

 abnormal than Cylindrocaulus and occurs in Burma, the Himalayas, Tonkin and Formosa. 

 The latter only occurs still further north, namely in China and Japan. Its species are the 

 only Aulacocyclinae known to have fused elytra. 



The Macrolininae fall into two series of genera, whose distribution must be considered 

 separately. The first of these comprises the genera Macrolinus and Pleurarius, whose 

 combined range covers the Oriental Region and Celebes, but does not extend into the 

 Papuan Sub-Region. Ceylon is occupied by species of Macrolinus which are closely allied; 

 to one another but differ in certain characters, common to all of them, from the remaining 



