Barriers to Dispersion of River Fishes 309 



portion of the water of Atlantic Creek crosses the meadow 

 to the other side. 



" Besides the channels already mentioned, there are several 

 more or less distinct ones that were dry at the time of our visit. 

 As already stated, the pass is a nearly level meadow covered 

 with a heavy growth of grass and many small willows one to 

 three feet high. While it is somewhat marshy in places it has 

 nothing of the nature of a lake about it. Of course, during 



Fig. 192. — Silver Surf-fish (\-iv\paTous) , Hypocritichthys analis (Agassiz). Monterey. 



wet weather the small springs at the borders of the meadow 

 would be stronger, but the important facts are that there is 

 no lake or even marsh there and that neither Atlantic nor 

 Pacific Creek has its rise in the meadow. Atlantic Creek, in 

 fact, comes into the pass as two good-sized streams from op- 

 posite directions and leaves it by at least four channels, thus 

 making an island of a considerable portion of the meadow. 

 And it is certain that there is, under ordinary circumstances, 

 a continuous waterway through Two-Ocean Pass of such a 

 character as to permit fishes to pass easily and readily from 

 Snake River over to the Yellowstone, or in the opposite direc- 

 tion. Indeed, it is quite possible, barring certain falls in the 

 Snake River, for a fish so inclined, to start at the mouth of the 

 Columbia, travel up that great river to its principal tributary, 

 the Snake, thence on through the long, tortuous course of that 

 stream, and, under the shadows of the Grand Teton, enter the 

 cold waters of Pacific Creek, by which it could journey on up to 



