1914-] F- H. GravEIvY : An Account of the Oriental Passalidae. 337 



Kaupioloides , Protomocoelus, Hyperplesthenus , Gnaphalocnemis , Plesthemùs , Gonatas, 

 Tarquinius and Leptaulax groups. Of these groups the first three and the last two appear 

 to be of most importance, and have been provisionally ranked as subfamilies, the remain- 

 der being put together into a single subfamily which takes its name from the genus 

 Gnaphalocnemis. Their rank cannot be finally settled without reference to American 

 and African species (pp. 193-4, 199 and 329). The genera and Oriental species of all 

 of them have been redefined (pp. 197, 199-204, 317-8, 329 and 318-326). 



2. External Morphology and Taxonomy. 



The pair of tubercles situated in the Pleurariinae, Aceraiinae, Macrolininae and 

 Gnaphalocneminae, between the central tubercle of the head and the processes of the 

 anterior margin, have been shown to be homologous with the inner pair of marginal pro- 

 cesses found in the Leptaulacinae ; and the terms inner and outer tubercles have been 

 consequently applied to the two pairs of processes found in all members of the second 

 section of the family (pp. 184-185). The use of these terms does not commit one to 

 any definite system of interpretation of the homologies of the head ; which is advan- 

 tageous, inasmuch as there is reason to believe that the whole of the upper surface of 

 the anterior part of the head between the supra-orbital ridges and in front of the 

 frontal ridges is frons, the whole of the clypeus being doubled beneath this out of sight ; 

 in which case these tubercles are not really processes of the clypeus as they have hitherto 

 been called (p. 185). 



Apart from this no criticism of the accepted homologies of different parts of 

 the body has been found necessary ; but considerable changes have been made in 

 the taxonomic values assigned to different parts (pp. 179-191), and it has been found 

 necessary to use all characters with much greater caution than has often been the case 

 in the past. As a result of this it has been found possible to define species with 

 a considerable degree of precision. Five species, however, stand out from all the rest 

 by reason of their remarkable variability, in size especially ; and certain structural 

 variations are corellated with variation in size, much as in the lyucanidae (pp. 262- 

 265). These species are Episphenus comptoni, Episphenus indicus, and Aceraius 

 grandis which appear respectively to be the dominant species of Aceraiinae in each 

 of the three divisions of the Oriental Region in which they occur ; and Leptaidax 

 dentatus and Leptaulax hicolor which are the dominant species of I^eptaulacinae 

 throughout the whole of this region (pp. 311-313). 



In the Aceraiinae and Gnaphalocneminae, the two subfamilies in which markedly 

 asymmetrical forms are found, the degree of asymmetry attained by a species appears 

 to be an index of the degree of specialization attained : and the dominant species of 

 a region is always the most markedly asymmetrical species found there (p. 312 ^). 



The nature of the asymmetry is somewhat different in different groups, and the 

 asymmetrical condition appears to have been evolved more or less independently in 

 each of them (fig. 7, p. 314). The evolution of a symmetrical LeptaiUax-like form, 



' As regards the Gnaphalocneminae see Gravely, 1914 (b). 



