_Chrosomus_ and _Notropis_ differ greatly in the length and convolution of the intestine. _Chrosomus_ has a long, coiled gut, which is crossed by the mid-ventral line eight or nine times; in _N. c. frontalis_, the intestine forms a flat, S-shaped loop that does not cross the mid-ventral line. In the two largest hybrids (KU 4170 and 4185), the gut is intermediate, crossing the mid-ventral line four times. In the smaller hybrid (KU 3872) the gut crosses the mid-ventral line twice but the configuration of the anterior loops indicates that the same intestinal convolutions that were found in the larger specimens would have developed in KU 3872 as the gut elongated with increase in size of the fish. Both Deep and Bluff creeks are clear, gravel-bottomed streams draining parts of the Flint Hills Area of Kansas. A description of Flint Hills streams and lists of fishes occurring in them have been published by Minckley (1956 and 1959), and by Minckley and Cross (1959). =_Chrosomus erythrogaster_ × _Semotilus atromaculatus_=: KU 2947 (28.0 mm. in standard length) from Mill Creek, Wabaunsee Co., Kansas, Sec. 30, T. 12S, R. 9E, Mar. 22, 1953. Compared in Table 2 with five specimens of _C. erythrogaster_, KU 2836 (27.2 to 31.0 mm., mean 28.5) from the same locality and of the same date as KU 2947 (above); and with five specimens of _S. atromaculatus_, KU 1954, 2499, 2703, and 2838 (25.5 to 31.1 mm., mean 28.9 mm.) from streams in the same area. This hybrid is intermediate between the two species in number of scales and pharyngeal teeth, and has a composite of the pigmentation found in the parental fishes (Table 2). For diagnostic purposes, greater importance is attached to the characters mentioned above than to proportional measurements, which are subject to considerable error because of the small size of the specimens. The few measurements that were taken indicate that this hybrid, like _C. erythrogaster_ × _N. c. frontalis_, has a larger head than do specimens of like size of either parental species. The enlarged head affects measurements obtained for other structures that are parts of the head; only the length of the upper jaw, which is greatly different in the parental species, is actually intermediate in KU 2947. Mill Creek is a clear stream, similar to Deep and Bluff creeks but somewhat larger. Mill Creek had an exceptionally large population of fishes at the time the hybrid was found, but _Chrosomus_ and _Semotilus_ were neither unusually common nor rare. Two other crosses, both of which have been described in the literature, also have been found in Mill Creek. These are _N. c. frontalis_ × _S. atromaculatus_, and _N. c. frontalis_ × _Notropis rubellus_ (Agassiz). TABLE 2. COMPARISON OF ONE SPECIMEN OF CHROSOMUS ERYTHROGASTER × SEMOTILUS ATROMACULATUS WITH SPECIMENS OF THE PARENTAL SPECIES (MEANS ARE ABOVE, RANGES IN PARENTHESES BELOW)