210 Journal of the Asiatic Society of Bengal. [June, 1914.] 



EXPLANATION OF PLATE XXIV. 



Muse 



nae 



locneminae, and all known species of the genus Episphenus, 1 

 are here figured diagrammatically , in a manner designed to show 

 the evolution of the five different types of asymmetry found 

 in the two subfamilies, and their geographical relations. All 

 forms connected by arrows with Episphenus moorei from 

 Ceylon, belong to the Aceraiinae, of which that species appears 

 to be the most primitive survivor; and all connected with the 

 Australian genera Pharochilus. Mastochilus and Episphenoides , 

 belong to the Gnaphalocneminae. In the former subfamily 

 only one type of asymmetry is found ; in the latter there are 

 four types, one of which is here indicated as derived directly 

 from the genus Kaupioloides and the other three from the 

 genus Hyperplesthenus. It should, however, be pointed out 

 that the genera Kaupioloides and Hyperplesthenus, with their 

 allies Aurelius.. Kaupiolus, and Labienus, although transitional 

 between the forms shown above and below them as regards the 

 characters at present under consideration, cannot be regarded 

 as representing actual ancestral types, on account of their 

 specialised metatsterna and certain other characters. But the 

 actual ancestors of all forms now living are clearly to be 

 sought for only as fossiLs ; and no fossil Passalids yet appear 

 to be known. 



The only known exceptions to the distribution shown 

 are : (I) a species of Episphenoides from New Guinea ; (2) one 

 or two species of Gonatas from the Sunda Islands ; (3) a pecies 

 of Gnaphalocnemis said to be found in Amboina ; and (4) the 

 genus Plesthenus whose anomalous distribution (in Australia 

 and Celebes) calls for further study. 



1 The species of this genu- from the Indian Peninsula and Ceylon 

 appear to have much the same zoogeographical value as the genera found 



in other parts of the Indo-Australian area. 



