330 Memoirs of the Indian Museum. [Vol. Ill, 



The evolution of a symmetrical Lcptaulax-like form from an asymmetrical ancestor, 

 suggests that the union of the inner tubercles with the anterior margin of the head 

 represents an even higher degree of specialization than does the asymmetrical condition . 

 The extraordinarily wide distribution and exceptional variability of the two dominant 

 species of Leptaitlax tend to support this suggestion. From which it may be inferred 

 that the Leptaulacinae are of comparatively recent origin, and that their scarcity in the 

 Indian Peninsula and Ceylon is due to the fact that they \i'\vi not yet had time fully 

 to establish themselves there. 



Whether the high degree of specialization thus indicated in Tarqitiimis will prove 

 sufficiently advantageous to its po.ssessor to enable it to become a dominant form 

 remains to be seen. At present the only known species of the genus appears to be 

 extremely rare. 



Before finally leaving the question of the many different forms assumed by 

 different species of Gnaphalocneminae and their allies, a further aspect may be 

 emphasized of the fact that in Pscmiepisphenus perplexus we have a specie§, obviously 

 of Australian and not Oriental extraction, whose mentum is indistinguishable from 

 that of an Oriental species. Its Australian ancestrj^ is indicated, apart from zoogeo- 

 graphical considerations, only by the form of the anterior margin of the head, 

 and this is the only structural indication of such ancestry that we could expect to 

 find in a species with a mentum of this form . 



If one species of Australian ancestry has such a mentum , there is no reason why 

 another should not have it also ; and the alteration needed in the form of the anterior 

 margin of the head of many Gnaphalocneminae to make them resemble the Aceraiinae 

 in this respect also, is no greater, and would be no more remarkable, than the 

 alteration that appears to have taken place in the evolution of Tarqiiiiiiiis. Two so- 

 called species, "Laches" infantilis and piurilis, Kaup, which I have been unable 

 to distinguish from Episphenus neelgherriensis, are recorded from Vanicoro (Santa 

 Cruz Islands) and the Aru Islands respectively. In the absence of any confirmation 

 of these records since the " species " were first described in 1871, the probability is, as 

 pointed out above (p. 284), that they are incorrect. Should either or both of them be 

 confirmed, however, convergence would, I consider, offer a much more plausible 

 explanation of such anomalous distribution, than migration in a manner utterly at 

 variance with that otherwise adopted throughout the Aceraiinae. It is, moreover, by 

 no means improbable that species may yet be found in Australian islands which, 

 though really allied to some group of Gnaphalocneminae, and distinct from any 

 known species of Aceraiinae, have, nevertheless, the characters of the latter rather 

 than of the former subfamily. 



10. APPENDIX IV -SUPPLEMENTARY CATALOGUE OF SPECIMENS IN 

 THE INDIAN MUSEUM COLLECTION. 

 Largely as a result of work done in European museums while the earlier parts of 

 this paper were going through the press the following additions have recently been 

 made to the Indian Museum collection. 



