216 R. R. MILLER 



abundance in southeastern United States (Miller, 1955), but which 

 was once more numerous west of the Continental Divide, whence 5 

 fossil species have been described (Miller, 1945b). 



Isolated Basin Drainages 



Certain isolated basins lying between the Lahontan, Bonneville, 

 and Colorado systems harbor a small but interesting remnant fish 

 fauna (Hubbs and Miller, 1948, pp. 51-67, 73-75). 



A group of valleys in northeastern Nevada share a peculiar 

 Rhi?tichthys-\ike dace, the only native fish in 4 of the 5 basins (Hubbs 

 and Miller, 1948, Map 1, Nos. 24-28, 30). The southernmost basin 

 (No. 30), Spring Valley, also harbors a species of Pantosteus, which 

 is related to species in all surrounding major w^atersheds; the common 

 ancestor of this sucker probably originated in the Great Basin. 



Lying north of the Lahontan basin are the Madeline Plains, site 

 of Pluvial Lake Madeline (Hubbs and Miller, 1948, Map 1, No. 33). 

 This region contains but a single fish, Rhinichthys osculus. The 

 remnant populations show remarkable uniformity and are ap- 

 parently indistinguishable from the Pit River form, suggesting that 

 Madeline Plains received its stock from that source (Hubbs and 

 Miller, 1948, p. 59). A very distinctive chub of the genus Siphateles 

 occurs in Alvord Valley, mostly in Oregon, and another species of 

 the same genus is known from Catlow and Guano valleys. Surprise 

 Valley, in northwestern Nevada, has an endemic sucker as well as 

 the noncommittal Rhinichthys, and the nearby Warner Valley, 

 mostly in Oregon, harbors Catostomus warnerensis (endemic), 

 Rhinichthys osculus, Siphateles hicolor, and was probably inhabited 

 by Salmo clarki (a Sacramento genus, Hesperoleucus, has likely been 

 introduced) . Too little is known about the affinities of these species 

 to enable one to draw reliable conclusions as to their origin. 



A number of isolated basins in south central Oregon, lying in the 

 desert region between the headwaters of Deschutes River and 

 Malheur Lake, were once united into Pluvial Fort Rock Lake 

 (Hubbs and Miller, 1948, p. 73). The Recent fauna includes Salmo 

 clarki, Rhinichthys osculus, and Siphateles hicolor, each of which has 

 relatives in adjacent watersheds. The fossil occurrence of Pacific 

 salmon (Oncorhynchus) establishes that the waters of this lake were 

 once directly connected to the ocean and the physiographic data 

 indicate that the connection was via Deschutes River. Study of the 



