for the years 1917-20. xiii 



be distinguished, superficial structural modifications in the species are 

 not of an extreme kind. The fauna is essentially similar to that of 

 other bodies of water in the same country. 



" Considered thus Lahe Bkva is a typical lake. Its fauna is very 

 similar to that of the lakes of North America in general facies and com- 

 position, except that it includes a distinct tropical (Oriental) element, 

 and also a deep-water element of northern origin. The deep-water 

 element closely resembles that of Swiss lakes. The species are different, 

 but many of the genera are the same, and modified in the same way, 

 thus illustrating the great principle of communal convergence. 



" Physical conditions in the Lahe of Tiberias are to some extent 

 abnormal, but not sufficiently so to affect the general character of the 

 fauna except in one particular, that they render it impossible for thin- 

 shelled molluscs to live in its water. Here again there is a marked 

 tropical (in this case Ethiopian) element in the fauna of a Palaearctic 

 lake. Its presence can be explained, as in Lake Biwa, on geographical 

 grounds. 



{d) Specialized LaJces. 



" Some of the largest lakes in the world (e.g., Lake Tanganyika 

 and Lake Baikal) are specialized lakes, having a highly modified fauna 

 distinct from that found elsewhere and due to physical and biological 

 factors, not always the same and too complicated in most instances 

 to be unravelled with our present knowledge. 



" The Inle Lake is such a lake on a small scale. Its fauna (includ' 

 ing that of other bodies of water directly connected with it) differs 

 considerably from that of other lakes, etc.. in Burma, particularly in 

 the fish and molluscs. . , . •. • • • • ." 



I omit further remarks on the Inle fauna, in order to avoid repetition. 



" A full account of the macroscopic fauna of the seven lakes is now 

 being published, or has already appeared, in Vol. XIV (Inle Lake) and 

 Vol. XVIII (Hamun-i-Helmand) of the " Records of the Indian 

 Museum "; in Vol. V (Chilka Lake) of the " Memoirs of the Indian 

 Museum " ; in Vol. IX (Lake of Tiberias) of the " Journal of the Asia- 

 tic Society of Bengal " ; and Vol. V (the Tale Sap, Tai Hu and Lake 

 Biwa) of the "Memoirs of the Asiatic Society of Bengal. " 



Taxonomy and Geographical Distribution of the Passalid Beetles.— 



In his paper in Vol. VII of the Memoirs of the Indian Museum 

 Dr. F. H. Gravely has brought to a conclusion, so far as is possible 

 at present, his investigations on the taxonomy and distribution of this 

 interesting family of beetles. He has dealt with the appearance of 

 asymmetry in the head and jaws of different sections of the Passalidae, 

 and has shown that certain facts in the geographical range of certain 

 genera and sub-families can be correlated closely with similar facts in 

 that of the Pedipalpi and the Mygalomorph spiders. The more highly 

 specialized species are often those nearest to the original centre of 

 distribution, the more primitive forms having, as it were, been expelled 

 furthest before extreme specialization took place. The western part 

 of the Malay Archipelago appears to have been an important centre 



