134 PROCEEDINGS OF THE ACADEMY OF [1883. 



on the fishes of the recent and pliocene lakes of the western 

 part of the great basin, and of the idaho pliocene lake. 



by e. d. cope. 



Preliminary Observations. 



The numerous lakes of the northwestern part of the Great 

 Basin present many points of interest to the geologist and biol- 

 ogist. The region which they occupy is one of comparativel3' 

 recent geological disturbance, so that their topographical features 

 may be regarded as of relatively modern origin. Their former 

 greater extent and intercommunication in groups has been clearly 

 pointed out by the geologists of the U. S. Survey of the Fortieth 

 Parallel ; and the species of fishes found in the pliocene and post- 

 pliocene deposits of the adjacent regions have been shown by 

 myself^ to be nearly allied to those now living in the present lakes. 



The geologists of the fortieth parallel have shown that a large 

 part of the present Territory of Utah was, during late tertiary 

 time, occupied by a large body of water, of which Salt Lake, 

 Utah Lake and Sevier Lake are the present representatives. To 

 this ancient sea they have given the name of Lake Bonneville. 

 They have also shown that the existing lakes of the western 

 region of Nevada were formerly united into an extensive body of 

 "water, to which they have given the name of Lake Lahontan. It 

 included the existing Walker's, Carson, Humboldt, P>'ramid and 

 Winnemucca Lakes. It is exceedingly probable that it will be 

 shown that a third lake existed in Oregon, north of the supposed 

 northern boundary of Lake Lahontan, which is now represented 

 by the Warner Lakes, Abert's Lake, Summer Lake and Silver 

 Lake, and probably by Harney's and Malheur Lakes on the eastern 

 side of the Oregon desert. As will be shown later, the larger 

 species of fishes found in such of these lakes as contain them, are 

 identical, and different from those of the lakes of the Bonneville 

 series. One species, the Catostomus tahoensis, is common to this 

 area and that of the true Lahontan Lakes (Tahoe and Pyramid), 

 and this Oregon lake may have been continuous with that of 

 Nevada, at a point some distance east of the mountains. Goose 

 Lake^ the Klamath Lakes, and doubtless Bhett and Clear Lakes, 



' Proceedings American Philosophical Society, Nov. 1870 and Dec. 1877. 



