248 FISHES. 



A peculiar feature of the North American Fish Fauna is 

 that it has retained, besides the Sturgeons and Lampreys, 

 representatives of two Ganoid families, Zepidosteus and Amia. 

 Both these genera existed in tertiary times : the former occurs 

 in tertiary deposits of Europe as well as North America, 

 whilst fossil remains of Amia have been found in the 

 Western Hemisphere only. 



It is difficult to account for the presence of the Amiurina 

 in North America. They form a well-marked division of the 

 Bagrina, which are well represented in Africa and the East 

 Indies, but absent in South America ; it is evident, therefore, 

 they should not be regarded as immigrants from the south, 

 as is the case with the Palaearctic Siluroids. Nor, again, 

 has the connection between South and North America been 

 established sufficiently long to admit of the supposition that 

 these Siluroids could have spread in the interval from the 

 south to the northern parts of the continent, for some of the 

 species are found as far north as Pine Islands Lake (54° 

 lat. N.)i 



III. SouTHEKN Zone. 



The boundaries of this zone have been indicated in the 

 description of the Equatorial Zone ; they overlap the southern 

 boundaries of the latter in South Australia and South 

 America, but we have not at jDresent the means of exactly 

 defining the limits to which southern types extend north- 

 wards. This zone includes Tasmania with at least a por- 

 tion of South-eastern Australia (Tasmanian sub-region), New 

 Zealand and the Auckland Islands (N'evj Zealand suh-rcgion), 

 and Chili, Patagonia, Terra del Fuego, and the Falkland 

 Islands {Fuegian sub-region). No freshwater fishes are known 



1 Leidy describes a Siluroid (Pimdodus) from tertiary deposits of Wyoming 

 Territory. " Coutrib. to the Extinct Vert. Fauna of the Western Territ. 

 1873," p. 193. 



