FRESHWATER FISH FAUNA 



201 



be a conservative group characteristic of lowland waters. The re- 

 maining 10 genera belong to the Catostominae ; 2 of its 3 tribes, the 

 Moxostomatini and Catostomini, contain over 80 per cent of the 

 known species of suckers. Five of the 14 genera are monotypic: 

 3 in eastern United States {Cydeptus, Lagochila, and Minytrema), 

 1 in western United States {Xyrauchen, Fig. 12), and 1 in China 



Fig. 10. Distribution of the sucker family, Catostomidae, in North 

 America and adjacent Siberia; one genus is endemic to China. Northern 

 limit between western side of Hudson Bay and Coppermine River from 

 Wynne-Edwards (1952, p. 18). 



(Myxocyprinus) . One genus in the East, Moxostoma, and 2 with 

 most of their species restricted to the West {Catostomus and Pan- 

 tosteus), account for 65 per cent of the modern species. 



The earliest possible fossil sucker remains (Hussakof, 1932, pp. 

 16-17) are from Eocene deposits of Central Asia and are probably 

 closest to the Chinese genus Myxocyprinus (Nelson, 1949, p. 566). 

 The earliest reliably dated remains of the family in North America 



