I9I4-] P- K- Gravely : An Account of the Oriental Passalidae. 317 



the Indian Peninsula with which it has hitherto been associated. In view of which 

 I have found it necessary to transfer B. cantori to the genus Ophrygonins. 



The monospecific genus Chilomazus is ahnost as closely related to the monospecific 

 genus Episphenus on the one hand, and to the genus Basilianus on the other, as are 

 the species Basilianus neelgherriensis and B. indicus to one another. Consequently, 

 as a genus consisting of only four species cannot be regarded as inconveniently large, 

 it seems best to unite all the species of Aceraiinae found in Ceylon and the Indian 

 Peninsula in a single genus, for which the name Episphenus must be retained. 

 The range of degrees of asymmetry found in this genus is very little greater than 

 that found in each of the genera Cetejus fed Analachcs. 



The species of Aceraiinae found on ;the other side of the Gangetic Plain are, 

 however, much more numerous; and, although transitional forms exist, the majority 

 either have almost symmetrical mandibles, or have both the lowest terminal and 

 anterior lower teeth on the right side quite rudimentary, the former tooth being normal 

 and the latter enlarged on the left side. The genus Ophrygonius must therefore be 

 defined so as to include all species of the former class, and the genus Aceraius so as to 

 include all species of the latter. 



The latter genus appears to have been derived from the former in at least two 

 different ways ; for the transitional species described above under the names Ophry- 

 gonius singapurae and Aceraius wallacei seem to be allied to quite a different section 

 of the genus Aceraius from that to which the transitional forms Aceraius acquidens 

 and A. minor are allied. 



Definitions, based on the structvire of the mandibles, could be framed so as to 

 include any of these four species in either genus ; so I have thought it best to follow 

 accepted definitions as far as possible, and to use the presence or absence of hair on 

 the sides of the elytra as the crucial test, although Aceraius wallacei is transitional in 

 this respect also, being much less hairy than most of the species belonging to the 

 genus in which I have had to place it. 



Four genera of Aceraiinae may then be recognized. They can be distinguished 

 from one another as follows : — 



j Inner tubercles separated by a space J— | as long as that 

 j separating outer tubercles . . 



\ Inner tubercles separated by a space j— i times as long as that 

 I separating outer tubercles . . . . 



Left outer tubercle acute, and little or no larger than right ; 

 or much larger and curved inwards, with its extremity rounded 

 rather than truncate, and never angular on the outer side in 

 front. Dentition complete in symmetrical species ; lowest ter- 

 minal tooth always present on both sides; right anterior lower 

 2' tooth smaller than left in the more highly asymmetrical species. 

 Left outer tubercle always larger than right, directed more or 

 less inwards, truncate distally, outer angle of truncation dis- 

 tinct, forming a more or less forwardly directed apex to the 

 tubercle; dentition complete, or both lowest terminal and 

 ^ anterior lower teeth reduced 



Tiberioides, Gravely, 



pp. 215 & 280. 



Episphenus, Kaup, 



pp. 217 & 281. 



