40 BULLETIN OF THE BUREAU OP FISHERIES. 



sion regarding the absence of an outlet fully explains the conditions here described. 

 Further than this the present distribution of certain species does not seem to be in 

 harmony with his interpretation of the geology, as will be indicated." 



Chasmistes cujus is a lacustrine form known only from Pyramid and Winnemucca 

 Lakes. The species lives in deep water beyond ocular observation except during the 

 short breeding season, when great numbers of adult individuals pass up the Truckee to 

 spawn. It is a large and clumsy fish (fig. 2) with relatively short fins and tail, not only 

 physically unfit, but apparently unable, to stem the current of a very rapid stream. During 

 the nuptial migration it does not go far beyond the great bend of the Truckee, selecting 

 its spawning beds before the turbulent water of the river is encountered. It will be 

 recalled that the only other species of the genus are found in Klamath and Utah lakes, 

 and attention is also directed to the fact that they are likewise lacustrine fishes with 

 habits similar to those of C. cujus. Complete desiccation of Pyramid and Winnemucca 

 I/akes at the present time would certainly bring about the extermination of this species,* 

 and it would, no doubt, have done so in the past. It therefore seems difficult to avoid 

 the conclusion that the presence of this form in the basin prevents the acceptance of any 

 hypothesis which does not recognize a complete continuity of Pyramid and Ivahontan 

 Lakes; and, moreover, an acceptable explanation of the present distribution of the 

 species of the genus Chasmistes must of necessity assume a continuity between Lahontan 

 and a still older lake or lakes which had at one time a channel connection with similar 

 large bodies of water located elsewhere in the Great Basin. Also this body of water, 

 continuous through a long period of time, must have been constantly fresh enough to 

 support plant and animal life. 



There is a trout indigenous to Pyramid and Winnemucca Lakes, Salmo smaragdiis 

 (described in the present paper), which can not be supposed to have recently differ- 

 entiated. Not much is known of the habits of the species beyond that it does not 

 appear in the rivers, and therefore apparently spawns in the lakes. The most nearly 

 related species is probably S. regalis of Lake Tahoe, although it is very different. The 

 turbulent Truckee appears to act as an impassable barrier to S. smaragdus, and there 

 is no reason to suppose that it could survive the dessication of Pyramid and Winnemucca 

 Lakes. 



A theory involving the introduction and differentiation of such species since 

 Quaternary times can scarcely be entertained at present, much less are we prepared to 

 accept the supposition that they have appeared here within the last 300 years. Where 

 there is any approximate measure of the time required in nature for the differentiation 

 of a species, it is not a matter of hundreds of years, but rather of a long geological period 

 of time. 



A large number of species found in the Lahontan system are generally distributed, 

 and it is therefore quite probable that these were introduced long before its separation 



a Recent discussions bearing more or less directly on this question may be noted here. 



Snyder, J. O.: The fishes of the Lahontan drainage system of Nevada and their relation to the geology of the region. Journal, 

 Washington Academy of Sciences, vol. iv, no. ii. p. 299; (extract), June 4, 1914. 



Jones. J. Claude: The geologic history of Lake Lahontan. Science, n. s. vol. xl, no. 1040, Dec. 4. 1914. 



Gale, Hoyt S.: Geologic history of Lake Lahontan, Science, n. s. vol. XLI, no. 1049, Feb. 5, 1915. 



6 The diversion of a considerable part of the Truckee may in the near (uture serve as a test for this supposition, unless the 

 fall of Pyramid Lake is followed by a deepening of the river channel, which in turn would cut off the water supply of Winne- 

 mucca Lake and thus maintain Pyramid at a level not far below that of the present. 



