The following species, common to both rivers, were more abundant in the Marais des Cygnes: gizzard shad, carp, sand shiner, black bullhead and white crappie. These species (with the exception of sand shiner) emphasize the fact that the Marais des Cygnes is a sluggish stream with large areas of mud bottom. Differences in the abundance of the sand shiner in the two rivers are part of taxonomic and distributional studies being conducted by Mr. Bernard C. Nelson. The following species were not consistently more abundant in one river than the other: big-mouthed buffalo, black buffalo, small-mouthed buffalo, short-headed redhorse, green sunfish, orange-spotted sunfish and orange-throated darter. These species, excepting the orange-throated darter and short-headed redhorse, occurred in a wide variety of habitats. FAUNAL CHANGES, 1957 THROUGH 1959 The following species increased in abundance from 1957 to 1959 (Tables 10 and 11): long-nosed gar, short-nosed gar, river carpsucker, creek chub, gravel chub, sucker-mouthed minnow, mountain minnow, blunt-nosed minnow, parrot minnow, stoneroller, stonecat, Neosho madtom, green sunfish, slender-headed darter, and orange-throated darter. These species can be separated into three groups, characteristic of different habitats but having in common a preference for permanent flow. One group, composed of long-nosed gar, short-nosed gar, river carpsucker, gravel chub, mountain minnow, parrot minnow, and Neosho madtom, prefers streams of moderate to large size. A second group composed of creek chub, sucker-mouthed minnow, stoneroller, and orange-throated darter occurs most abundantly in small, permanent streams. The green sunfish may be included here on the basis of its abundance at the upper Neosho station; however, this is a pioneer species and does not require permanent flow. The third group is characteristic of continuously flowing water, but in both upstream and downstream situations. The species in this group (blunt-nosed minnow, stonecat, and slender-headed darter), increased in response to a resumption of permanent flow, but did not respond as quickly as did channel catfish, flatheads and freshwater drum, which are discussed subsequently. The fact that riffle-insects were abundant throughout my study convinces me that food was not a limiting factor in the re-establishment of the fish-fauna on riffles of the Neosho River. The following species decreased in abundance during my study (Tables 10 and 11): gizzard shad, carp, rosy-faced shiner, blunt-faced shiner, red shiner, mimic shiner, black bullhead, yellow bullhead, channel catfish, flathead, slender madtom, tadpole madtom, freckled madtom, spotted bass, largemouth, black crappie, fan-tailed darter, and freshwater drum.