2 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 65 



Stillwater. The cave is about 50 feet above the floor of the old 

 Lake Lahontan and probably 350 feet below the highest beach line. 

 The fossils were 6 feet below the surface of the ground. The walls 

 of the cave v>'ere encrusted with tufa rock deposited by the old lake. 

 The specimens were plentiful, in a layer not over one foot wide." 



The question of the age of this deposit has been referred to Prof. 

 J. C. Jones, of the Universit}^ of Nevada, who decides, after per- 

 sonal examination of the deposits, that " the fish skeletons were de- 

 posited in Lahontan-time and probably not over a thousand or fifteen 

 hundred years in age, if my conclusion as to the age of Lake Lahon- 

 tan are correct. , . . Their living relatives should be found in 

 Pyramid Lake, which is a remnant of Lake Lahontan. The greater 

 bulk of the diatomaceous earth in Nevada was deposited during 

 Middle Miocene time in western Nevada. The Lake Lahontan beds 

 contain verj^ little diatomaceous earth as the waters were rather 

 muddy, but it is possible that in the protected cave, the diatoms 

 lived in water clear enough to have formed rather pure diatomaceous 

 earth of Lahontan age." 



The specimens here figured are numbered 10905-10907 in the col- 

 lection of the United States National Museum. Cotypes are in the 

 collection of Stanford University. This description is drawn from 

 the entire series, not one having all the fins complete. The species 

 is evidently a Cottus^ and it may be identical with one or more of the 

 four fossil species described by Cope in 1883, from Pliocene deposits 

 of the former Lake Idaho. (Coitus dlvmicatus, D. jwntlfex, D. 

 hypoceras and C. eryptoti'e'nvus.) These are all known only as 

 many detached preopercles, and can not well be contrasted with 

 Cottus heldingi. 



The last named species, first described (in 1891) from Lake Tahoe 

 and Donner Lake, is now found in all suitable waters throughout the 

 Lahontan Basin, and is recorded from various localities in the upper 

 Columbia (Jordan and Evermann). The only apparent differences 

 are these : in Cottus heldingi the preopercular spine is simple and 

 the ventral rays seem a little more slender than in the fossil. 



EXPLANATION OF PLATE. 



Fossil examples of Cottus heldingi Eigenmann and Eigeumaun. Upper views 

 are ventral aspects and the lower ones show dorsal views. Natural size. 



