DISTRIBUTION OF FRESH-WATER FISHES. 391 



donts) by one hundred and ten species. As to their geographical 

 distribution, two primary zones might be recognised : the northern, 

 corresponding largely to North America and Temperate Eurasia, 

 characterised by the presence of sturgeons, salmonoids, pikes, and 

 numerous carps, with only a feeble development of the cat-flshes ; 

 and the southern or tropical zone, comprising the Indian, Ethio- 

 pian, Neotropical, and Australian regions of zoogeographers, char- 

 acterised by a special development of the cat-fishes. The fol- 

 lowing scheme for the classification of the southern zone has been 

 proposed by Dr. Giinther : 



Ctpbinoid Division. — Characterised by presence of Cyprinidae 

 and Labyrinthici. 



1. Indian Region, 625 Species. — Characterised by Ophiocephalidaa 

 and MastacembelidsB. Cobitoids numerous. 



2. Afriam Region, S5S Species. — Characterised by lung-fishes 

 (Protopterus) and ganoids (Polypterus, Calamoichthys). Chromoids 

 and characinoids numerous. Cobitoids absent. 



AcypBiNoiD Division. — Characterised by absence of Cyprinidse 

 and Labyrinthici. 



1. Tropical American Region, 672 Species. — Characterised by 

 lung-fishes (Lepidosiren). Chromoids and characinoids numerous. 

 Gymnotidae (electric eels). 



3. Tropical Paeijic Region, 36 Species. — Characterised by lung- 

 fishes (Ceratodus Forsteri and C. miolepis, from the waters of 

 Queensland, Australia). Chromoids and characinoids absent. 



The eastern and western divisions of the northern zone, with 

 some three hundred and sixty and three hundred and forty species 

 respectively, are very closely related to each other, not only through 

 the preponderance of types that are common to both regions, but 

 in the possession, as has already been seen, of a number of identical 

 species. Two genera of ganoids not found in Eurasia, Lepidosteus 

 and Amia, serve to characterise the American ichthyic fauna, which 

 is further distinguished from its trans-Atlantic correspondent in 

 the special development of the suckers (Catostomidae) and in the 

 absence of cobitoids and barbels (Barbus). 



An Antarctic zone, made to include New Zealand, Tasmania 

 (with a portion of Southeast Australia), the Falkland Islands, Tierra 

 del Fuego, Patagonia, and Chili, whose faunas are very intimately 

 related to one another, is recognised by some authors, but the num- 



