FRESHWATER FISH FAUNA 199 



deridae), they form a North American group known from Eocene 

 to Recent (Fig. 7). 



The centrarchids, or sunfishes, comprise a compact family of 

 about 11 genera and 30 species, which, except for the rehct genus 

 Archoplites of California (Fig. 8), are confined to eastern North 

 America (Fig. 9). The present center of distribution is in the middle 

 and lower Mississippi Valley. Relatively numerous fossils are 

 recorded from Oligocene to Pleistocene deposits of North America ; 

 whether or not the Green River Eocene genus Priscacara is a sunfish 

 has not been conclusively shown, although Regan (1915, p. 106) un- 

 questionably referred it to the Centrarchidae. This freshwater 

 group dates from the early Cenozoic and is closely related to the sea 

 basses (Serranidae). Since as a whole sunfishes are characteristic of 

 lowland waters, the sole survivor in the West presumably attained 

 its present distribution prior to the formation of the Rocky Moun- 

 tains and Sierra Nevada Ranges. 



The two remaining families, the minnows and suckers, account 

 for 95 of the 99 species of primary freshwater fishes in western 

 North America. The suckers, a compact group of 14 living genera^ 

 and about 80 species, are known fossil and Recent from eastern 

 Asia and Alaska, as well as from eastern and western North Amer- 

 ica. In the New Worid (Fig. 10) they range southward on the 

 Atlantic slope to northern Guatemala {Ictiobus, Rio Usumacinta) 

 and on the Pacific versant to western Mexico {Moxostoma, Rio 

 Armeria, Jalisco). In the Old Worid there are but two representa- 

 tives, an ancient, monotypic genus in China {Myxocyprinus) and 

 Catostomus catostomus, in eastern Siberia, representing a recent 

 invasion of a species widespread in northern North America (Dar- 

 lington, 1957, p. 31, Fig. 9). In the most recent treatment (Nelson, 

 1948, 1949), division of the family into three subfamilies (Fig. 11) 

 has been made largely on the basis of the morphology of the four 

 highly modified anterior vertebrae (the Weberian apparatus) that 

 connects the gas bladder with the middle ear. The Cycleptinae, with 

 a primitive genus in each continent, might justifiably be segregated 

 as two subfamilies with Cycelptiis as the North American and 

 Myxocyprinus as the Asian representative. The Ictiobinae includes 

 but 2 genera and 9 species in eastern North America and appears to 



1 The following are regarded as synonyms: Deltistes = Catostomus; Megapharynx and 

 Placopharynx = Moxostoma; Megastomatobtis = Ictiobus. 



