568 MB. F. DAY ON THE QEOGKAPHICAL 



0. gachua is found at the Andaman Islands. Genus Channa is 

 found in Ceylon and China, but absent from intermediate loca- 

 lities. Poly acanthus signatus has only been taken in Ceylon and 

 Java. Genus Etroplus through the Ceylonese subregion, and an 

 allied genus in Madagascar. Genus Silurus, Himalayas to Akyab, 

 Tenasserim, Cochin China, the Malay archipelago and beyond ; also 

 Eastern Europe and Turkestan, and along the Malabar Ghauts ; 

 but is not found in the Hindustan subregion. Exostoma along the 

 Himalayas to Assam, Pegu, Tenasserim, and the confines of China. 

 Haplocliilus fancliax from the Hindustan subregion, through 

 Burma and Siam to the islands of the Malay archipelago, and is also 

 common at the Andaman Islands. 8capModon from "Western 

 Asia to the Sind and the Punjab, and along the western Ghauts, 

 but is otherwise absent from India. Nuria danrica extends from 

 the Ceylonese and Hindustan subregions to Burma and the Nico- 

 bars; but is absent from the islands of the Malay archipelago. 

 Somaloptera Brucei and H. maculata are common to the Hima- 

 layas and the western Ghauts of India, but are absent from the 

 Hindustan subregion. 



The preceding and other somewhat similar instances ofier a 

 wide field for conjecture as to how these fishes came in such loca- 

 lities, and by what means they have spread to more distant 

 districts ; but before ofiering any remarks on the subject, it 

 will be necessary to digress a little, and refer to the opinions of 

 others who have written on this question. 



Geologists have pointed out that the plains of Hindustan are 

 Tertiai'y with a few isolated patches of Secondary rocks, and the 

 peninsula in the later Tertiary epoch was an island, an arm of the 

 sea existing along the present deltas of the Ganges and the 

 Indus. Ceylon and South India consist (at least on the western 

 Ghauts) mainly of granitic and old metamorphic rocks ; and they 

 probably formed during a portion of the Tertiary period a large 

 continent, the zoology of which had a close affinity to that of the 

 Malayan region. 



Dr. Stoliczka observed that " it does not appear improbable 

 that the fauna of India was at some remote period chiefly or alto- 

 gether Malayan, and that it had been more or less destroyed in 

 those parts which were affected by the enormous volcanic erup- 

 tions, characterized as the Trappean formation of Central and 

 N.W. India. It must have been somewhere about that time 

 when a communication was established between India and Africa, 



