]<ils.| F. If. (Iravklv: /'assalidae of the World. 125 



tliidugli tlio fusion (if the two lowest tpnninal teeth. In Indo-Au.stralian .subfamilies it is 

 always associated with cophalic asymmetry and never with the loss of the habit of flight, 

 .and comes about through the fusion of the anterior lower and lowest terminal teeth 

 (pp. 9-IO, fig. ii). 



The lo.ss of the habit of (light appears to allow of greater .specialization of the wings a.s 

 stridulating organs. It pioduces definite structural modifications in the insect (pp. 4-5). 

 The following genera contain, .so far as is known, only flightless forms ■.—Ciflindroratdus, 

 Flatyrerres, Pleurariiis, Proodejoides, Procidcjns, Procnhdus, Proculus, Pseudnranlhus 

 and PuhUus. The following species are also flightless -.—Labienus molnccanus and gigas, 

 Macrollniis obesus and t(rsus, Passnlus quitensis and V index synelytris. 



The structure of the male genital tube is almost uniform throughout the family. 

 The genera of Aulacocyclinae other than Ceracupes and Cylindrocuulus differ, however, from 

 the rest of the family in that the basal piece and lateral lobes are represented by one 

 undivided plate (p. 5). 



The central tubercle is u.sually larger in females than in males in species in which 

 it varies greatly in size (p. 5). 



2. Classification. 



Seven sulifainilio have been recognized, of which one. the Aulacocyclinae, confined to 

 the Indo- Australian area with China and Japan, is somewliat widely removed from all 

 the others (p. 9). Two others are confiiu'd to the Indo-Australian area. These are 

 distinguished from American and Ethiopian sul)lainili.'s by the structure of the mandibles 

 (p. 9). The Ethiopian subfamily is distinguished from tlie four American ones by the 

 structure of the anterior margin of the head (pp. lo-i i). 



The number of genera has been greatly reduced. Specific synonymy has not been dealt 

 with, but there can be little doulit that a similar reduction is required in the number of 

 species. 



3. Geographical Di,strib>(tion. 



Passalidae appear to flourish only under more or less moi.st tropical conditions. 



American, Ethiopian and Indo-Australian forms belong respectively to different 

 subfamilies, probably without exception (pp. 9-12). 



The group of Macrolininae with strong asymmetrical tendencies is of .special zoogeo- 

 graphical interest. Its most primitive species inhabit Ceylon and Australia. These 

 are closely allied to one another but give rise to divergent lines of descent, confined 

 respectively to the Oriental Region with Celebes, and to the Australian Region. Both these 

 regions are composed of a series of smaller areas, each characterized by a distinct Pa.ssalid 

 fauna, which is more highly specialized in those nearer to Celebes than in those further 

 away. These areas are : in the Oriental Region— Ceylon, the Indian Peninsula, the 

 Indo-Chine.se Subregion and the .Malayan Subregion ; and in the Austrahan Region — 

 Au.stralia, New (hiinea and the Moluccas (pp. 120-124). These facts bear out the 

 suggestion (Oravely, 1913, p- 204) that conditions towards the centre of the Archipelago are 

 peculiarly favourable for evolution, and that as more and more highly specialized forms 

 have arisen there, they have migrated outwards, driving before them the less highly 



