129 



Only 10 species are characteristic of tlie western belt, tlie most characteristic 

 ones being the cut-throat trout, Williamson's whitefish, the blob, the grayling, the 

 long-nosed sucker, Jordan's sucker, and the western dace. 



Only 45 species are known from North Dakota, Montana, Wyoming and 

 Colorado. On the other hand, Missouri and the small part of Iowa drained by 

 the Missouri, furnishes 94 species, or, if we include the narrow timbered and 

 abundantly watered strip of eastern Kansas, Nebraska and South Dakota, we have 

 about 100 species occurring in this eastern or lower belt of the Missouri Basin. 

 The middle belt has such characteristic s])ecies as Platytjoblo (jracilk, Hybopnis 

 gelidug, Hi/bof/ nat has nuc halts eranxi, and the like. P'ew if any of these are confine<l 

 to this belt, but they probably all extend more or less into the lower and upper 

 belts. 



In the lower portion of the middle belt is found the limit in the western 

 extension of spiny-rayed fishes. West of the 96th meridian, which is approxi- 

 mately the eastern boundary of Nebraska and the Dakotas, not over a dozen 

 species of spiny-rayed fishes are known to occur. This fact becomes interesting 

 when we recall that a single small creek in Indiana (Bean Blossom Creek, 

 Monroe County*', is known to contain not fewer than thirty-five species of spiny- 

 rayed fishes, and from the streams of Indiana alone we know at least fifty-one 

 species of that group — nearly as many as the totalnumber of species found in the 

 entire fish-fauna of the Missouri basin west of the 98th meridian. 



In the Missouri itself and in its larger tributaries are found sucli large river 

 species as Poli/odon "iiathula, Scaphirhynchus platorynchus, Leplnps olivaris, Ictalums 

 puncfitus, species of Ictiobm, and the like; but in the smaller streams Ca'ostomus, 

 Hybogudthus and Nolropis are the principal genera represented. Micropterus, 

 Perca, Leponiis, and Etheostoma are not rare on the eastern edge of this region, but 

 they become more and more rare as we go westward and very soon disappear 

 altogether. Perca has not yet been found west of Mitchell, S. D., 98° west; 

 Micropt"' tiA has rot been found west of Ravenna, Neb., 98° '.W W., and it is not 

 likely that it occurs naturally even that far west. 



Of the four darteis whose range extends farthest west in this basin, Bole.osama 

 niyrum reaches only to Mitchell, S. D., Hadroptervs aspro to Ewing, Neb., 98° 20^ 

 W., EtheoMoma louoe extends still further west, having been found by us at 

 Valentine, Neb., 100° 30' W., while Boleichthys exdis, a somewhat doubtful 

 species, was found even a little farther west in North Dakota. 



The Flat-headed Chub is pre-eminently the characteristic fish of the shallow, 

 alkali streams of the middle Missouri basin, and shows better than any other the 



Eigenmann and Fordice, Proc Phil. Acad. Sci. 1885. 

 9 



