10 INDIAN FRESH-WATER FISHES. 



congregation, so that in the majority of cases there is 

 little difficulty in deciding the family to which a fish 

 belongs. Some species there are certainly which lie 

 on the borderland between one family and another, as 

 must be expected, but these cases are comparatively 

 few. 



Some families inhabit the salt water exclusively ; 

 some are confined, as, for instance, the Cypriniclse, to 

 fresh waters. Some, as the Salmonidse, are only 

 found in the temperate regions of the Northern Hemi- 

 sphere, being apparently unable to pass the heated 

 waters of the tropics, while others are only found in 

 tropical regions, being unable to exist in the colder 

 climates. Other families again have representatives in 

 all parts of the globe. 



In the fresh waters of India two families are most 

 plentifully represented, viz., the Cyprinidse, or carp 

 family, and the Siluridse. The latter are easily re- 

 cognised by wanting scales. 



The Ophiocephalidse, or Snake-headed fishes, have 

 also a good many species in India ; and many other 

 families are represented by one or two species, but 

 perhaps nine-tenths of the fishes that are usually met 

 with belong to one or other of the two first-mentioned 

 families. 



(As an example among large animals of what con- 

 stitutes a family, we may instance the Family 

 BovidaB, which includes in it, sheep, goats, oxen, 

 antelope, bison, etc., each of these forming a separate 

 genus.) 



