270 



SCIENCE 



[N. S. Vol. XXVII. No. 685 



Since the two systems are widely isolated, 

 one can explain ihe identity of their faunas in 

 so far as it exists, only by the assumption that 

 an intermingling of their waters occurred at 

 some past time. Several years ago attention 

 was directed to a probable connection between 



Map of the Russian River basin and parts of the 

 Sacramento and neighboring rivers. 



these basins, no reference being made at the 

 time to their faunas. Lawson' in 1894 made 

 a statement to the effect that at one time the 

 Russian River, instead of turning abruptly 



' Lawson, Andrew C, " The Greomorphogeny of 

 the Coast of Northern California," Bull. Dept. 

 Geol. Univ. of Cal., I., p. 269. 



westward to the ocean, continued its south- 

 ward course through an uninterrupted valley 

 to the region now occupied by San Pablo Bay. 

 It would thus have established a main channel 

 connection with the Sacramento, the union 

 being perfect in case of a slight elevation of 

 the coast which probably prevailed at that 

 time. In this connection it should be em- 

 phasized that whatever may have been the 

 agency for bringing about a passage between 

 the two systems, it was apparently not able to 

 transfer a complete representation of the Sac- 

 ramento fauna to the Russian River. There 

 are among the Sacramento fishes a consider- 

 able number of species not known in the 

 Russian River, of which may be mentioned 

 Orthodon microlepidotus, Lavinea exilicauda, 

 Pogonichthys macrolepidoius and Leuciscus 

 crassicauda, all strictly fluvial. Concerning 

 these species two facts should be noted as 

 having a possible bearing on the method by 

 which the Russian River received its fish 

 fauna: (1) they are indigenous to certain 

 small streams which flow into San Francisco 

 Bay' and they have also found their way from 

 thence southward* into certain small coastal 

 streams, where they are now abundantly able 

 to maintain themselves ; (2) they are such 

 forms as inhabit the lower courses of the 

 rivers, seemingly preferring the warmer, deep- 

 er and more quiet waters of the main channel. 

 Now, if the Russian River received its fauna 

 from the Sacramento through a main channel 

 connection, as may be inferred from Lawson's 

 statement, we should expect to find among its 

 species the same channel fishes as inhabit the 

 Sacramento and the smaller streams flowing 

 into San Francisco Bay. They are absent, 

 however. That they were once introduced 

 and have since become extinct seems scarcely 

 probable, since they are now living in the small 

 streams referred to, under conditions appar- 

 ently similar to those prevailing in the Rus- 



' Snyder, J. O., " Notes on the Fishes of the 

 Streams flowing into San Franeicco Bay, Cali- 

 fornia," Rept. Com. Fish., Dept. Com. and Labor, 

 1904, p. 327. 



' Branner, J. C, " A Drainage Peculiarity of 

 the Santa Clara Valley Affecting Fresh-water 

 Faunas," Jour. Oeol., XV., No. 1. 



