INDIAN REGION. 223 



Cyprinoids, of whicli the former show a contingent of about 

 200, and the latter of about 330 species. The combined 

 development of those two families, and their undue pre- 

 ponderance over the other, freshwater types, is therefore the 

 principal characteristic of the Indian region. The second 

 important character of its fauna is the apparently total 

 absence of Ganoid and Cyclostomous fishes. Every other 

 region has representatives of either Ganoids or Cyclostomes, 

 some of both. However, attention has been directed to the 

 remarkable coincidence of the geographical distribution of 

 the Sirenidce and Osteoglossidce, and as the latter family is 

 represented in Sumatra and Borneo, it may be reasonably 

 expected that a Dipnoous form will be found to accom- 

 pany it. The distribution of the Sirenidce and Osteoglossidce 

 is as follows : — 



Tropical America. 



Lepidosiren paradoxa. 



Osteoglossum bicirrhosum. 

 Arapaima gigas. 



Tropical Australia. 



Ceratodus forsteri. I Osteoglossum leichardti. 



Ceratodus miolepis. I 



East Indian Archipelago. 

 1 I Osteoglossum formosum. 



Tropical Africa. 

 Protopterus annectens. | Heterotis niloticus. 



Not only are the corresponding species found within the 

 same region, but also in the same river systems ; and although 

 such a connection may and must be partly due to a similarity 

 of habit, yet the identity of this singular distribution is so 

 striking that it can only be accounted for by assuming that 

 the Osteoglossidce are one of the earliest Teleosteous types 

 which have been contemporaries of and have accompanied 



