418 Journal of the Asiatic Society of Bengal. [November, 1914. 



lution of the ground-dwelling genera of Aviculariinae centred in 

 the transgangetic area. 



In comparing the distribution of the Aviculariinae des- 

 cribed above, with that of the Aceraiinae described in my last 

 communication to this Society, the first point to be noted is 

 that the evidence in the present case does not relate to forms 

 found south or east of the Indian Empire and Ceylon, and that 

 whether the Aviculariine fauna of continental Asia beyond the 

 Ganges has originated there or in the Archipelago must be 

 left an open question. 



Secondly, it must be pointed out that in the Aviculariinae 

 equally primitive forms—as far as I am at present able to 

 judge— are found in both sides of the Ganges and on both 

 sides of the Palk Strait. Forms sufficiently primitive to 

 connect the faunas found on either side of the Ganges are not, 

 as in the Aceraiinae, confined to Ceylon, nor do they appear 

 to be more common in Ceylon than in India. But they are far 



more common in 



West 



Southern India, than in the countries beyond the Ganges. 



In dealing with the Aviculariinae it is evident that no dis- 

 tinction can be drawn between the faunas of India and Ceylon. 

 When this has been allowed for the similarity between the dis- 

 tribution of the Aviculariinae and Aceraiinae is very close. The 

 gradual increase in specialization seen in the relatively primitive 

 Indian and Ceylonese Ischnocoleae and Thrigmopoeeae finds its 

 parallel in the gradual increase in specialization seen in the rela- 

 tively primitive Indian and Ceylonese genus Episphenus. And 

 the much higher degree of specialization reached in the essen- 

 tially transgangetic group Selenocosmieae than in the Ischno- 

 coleae and Thrigmopoeeae, finds its parallel in the much higher 

 degree of specialization reached by the genus Aceraius than by 

 the genus Episphenus. 



With regard to the latter parallel, however, certain differ- 

 ences must not be allowed to escape notice. Firstly, al- 

 though the derivation of the genus Chilobrachys from Sele- 

 nocosmia can be paralleled by the derivation of the genus 

 Aceraius from the genus Ophrygonius, the transgangetic Avi- 

 culariine series can be traced back to a primitive group, the 

 Ischnocoleae, which, though very much rarer in the countries 

 beyond the Gauges than in India and Ceylon, are not extinct 

 there ; whereas the most primitive existing representatives of 

 the Aceraiine series are confined to Ceylon. ^Secondly, the most 

 highly specialized genus of the former series has already spread 

 into the Indian Peninsula and Ceylon; whereas that of the 

 latter series has not. Thirdly, the Poecilotherieae, which appear 

 to be derived from Indian or Ceylonese ancestors as a result of 

 a change in their mode for life, find no parallel, so far as I can 

 see, among the Aceraiinae. The position of the Ornithoctoneae 



