252 FISHES. 



1. Species of Bajidm ifiaja, Trygon) prefer the mouths of 

 rivers, probably because the muddy or sandy bottom offers 

 the most suitable conditions for fishes which can feed on the 

 bottom only ; such brackish water species belong chiefly to 

 the Equatorial Zone, some having taken up their abode 

 entirely in fresh water (South American Trygons). 



2. Ambassis, a Percoid genus, consisting of numerous small 

 species, iahabiting the shores of the tropical parts of the 

 Indian Ocean and the coasts of Tropical Australia. Many 

 species enter, and all seek the neighbourhood of, fresh water ; 

 hence they disappear in the islands of the Pacific, and are 

 scarce in the Eed Sea. 



3. Therapon, with the same distribution as the former. 



4. Numerous Scicenidce of the Equatorial Zone. 



5. The Polynemidm, chiefly inhabitants of brackish water 

 of the Equatorial Zone, most developed in the Indian 

 region, and scarce in the Tropical Pacific. 



6. Numerous species of Qaratix, (or Horse Mackerels) of 

 the Equatorial Zone. 



7. Nearly all species of Gastrosteus enter brackish water, 

 G. spinachia being almost exclusively confined to it : 

 Northern Zone. 



8. The most important genera of the Gobies {Gohiina) : 

 Gohius (nearly cosmopolitan), Sicydium, BoleopMhalmus, Peri- 

 ophthalmus, Meotris (equatorial). Many of the species are 

 entirely confined to fresh water. 



9. The Amhlyopina, similar to the Gobies, but with more 

 elongated body : Tropical Indo-Pacific. 



10. The Trypauchenina : Coasts of the Indian region. 



11. Many species of Elennius, of which several are found 

 far inland in fresh waters — for instance in North Italy, in the 

 Lake of Galilee, in the eastern parts of Asia Minor. 



12. The majority oi Atherinidce, and 



