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physical, chemical and biological features of the streams and lakes of the 

 region under consideration, for these in their various phases are the forces 

 or conditions which constitute the fish- environment, and which determine 

 the abundance, condition and distribution of the fish life of each hydro- 

 graphic basin. 



While carrying on these investigations, I spent the greater part of the 

 month of October in and about the Black Hills, and it is to some of the 

 biologic characteristics of that region that I desire to call your attention. 



The Black Hills are, as you are aware, an isolated mountain group lying 

 in southwestern South Dakota and eastern Wyoming. These Hills lie 

 wholly within the basin of the Cheyenne River, which is formed by the 

 union of the North and South Forks. The North Fork of the Cheyenne, 

 or the Belle Fourche, as it is usually called, has its rise west of the Hills, 

 flows around them on the north side, and to the eastward joins the South 

 Fork which also rises west of the Hills and sweeps around them to the 

 southward in a wide curve very much like that of the Belle Fourche on 

 the north. 



The immediate drainage of the Hills is by means of numerous smaller 

 streams, nearly all of which flow eastward in approximately parallel 

 courses to one or the other of the two Forks, those flowing into the Belle 

 Fourche doing so from the right bank, while those reaching the South 

 Fork flow into it from the left bank. During our stay in this region we 

 made collections of fishes in the following streams : Middle, Sand, Red- 

 water, Crow, Chicken, Spearfish. Whitewood, Beaver, Rapid, Flk, Fall, 

 Warm. Cold, Minnekahta, and Cottonwood creeks, the Belle Fourche and 

 the South Fork of the Cheyenne, and in Montana and Cox's lakes, nearly 

 all of which are well supplied with certain species of fishes. The study of 

 these collections has opened up a number of interesting questions in geo- 

 graphic distribution. 



The fish fauna of that portion of the Missouri system lying in and about 

 the Black Hills is peculiarly restricted in its character. The fifteen 

 species contained in this collection, — and no other species has ever been 

 reported from any definite locality of this region, — represent but four 

 families, viz.: two catfishes, four suckers, eight minnows, and one member 

 of the codfish family. Fight of the fifteen species belong to one family, 

 the Cyprinidx. Not a single species of spiny-rayed fish has been found in 

 the streams about the Hills, and it is not likely that any will be found 

 there. Many of the streams in or near the Hills would apparently turn- 



