This fauna includes fishes living not only in the main streams but also in the lower parts of the larger tributaries of these streams. The fauna was comparatively rich: in the main stream of Big Caney River 39 species were taken, in Grouse Creek 35 species, in the Walnut River main stream 21 species, and in the Arkansas River 19 species. It has been pointed out that large rivers such as the Walnut and Arkansas have been subjected to greater direct and indirect modification by man, possibly resulting in a less diverse fauna than would otherwise occur in these streams. At present, there is a paucity of ecological niches in the upland tributaries and large rivers, as compared with streams of intermediate size. Fishes typical of the Caney-Elk-Grouse association were _Notropis umbratilis_, _Lepomis megalotis_, _Lepomis humilis_, _Labidesthes sicculus_, _Fundulus notatus_, and the two species of _Micropterus (Micropterus punctulatus_ was not taken in Grouse Creek). _Upland Tributary Fauna_ Tributary faunas were divisible into two categories: (1) Those of the Walnut River and Grouse Creek (intermittency was severe, species were few, with _Ictalurus melas_ and _Lepomis cyanellus_ predominating); (2) those of Big Caney River (stream-flow was more stable, and eastern fishes, some of which have Ozarkian affinities, occurred in greater abundance than in any other part of the area surveyed). In the latter streams _Campostoma anomalum_ and _Etheostoma spectabile_ usually were dominant. _Pimephales notatus_, _Notropis volucellus_, _N. camurus_, _N. boops_, and _N. rubellus_ characteristically occurred. _Notropis lutrensis_ was sparsely represented in flowing tributaries. _Notropis umbratilis_, which seems to prefer habitats intermediate between those of _Notropis lutrensis_ and Ozarkian shiners, was usually represented. Deep-bodied suckers and carp were not taken in upland tributaries but _Moxostoma erythrurum_ was common and _Minytrema melanops_ was taken. The kinds and numbers of shiners (_Notropis_) taken at different points along Grouse Creek seem significant. _N. lutrensis_ and _N. umbratilis_ occurred throughout the stream but were rare in sluggish areas where populations of _Gambusia affinis_, _Fundulus notatus_, and _Labidesthes sicculus_ flourished. At the lowermost station _Notropis percobromus_ and _N. buchanani_ were taken; these were not present in other collections. In the uppermost stations where water remained plentiful, _N. boops_ and _N. volucellus_ were taken, and _N. rubellus_ has been recorded.