Another specimen of _C. a. plumbeum_ × _S. atromaculatus_ (KU 4841, 39.3 mm. in standard length) was taken in the North Platte River at Lisco, Garden County, Nebraska, on September 11, 1959. That specimen has 7 anal rays and 52 scales in the lateral line; otherwise, it is similar to the three hybrids described above. =_Gila nigrescens_ × _Rhinichthys cataractae_=: KU 4253 (a male, 60.6 mm. in standard length), from New Mexico, Bernalillo County, Rio Grande 12 mi. S Bernalillo on U. S. Highway 85 (Corraleo Bridge). Compared in Table 4 with six specimens of _G. nigrescens_: KU 4251, 4254, and 4262 (63.1-72.4 mm. in standard length, mean 66.4 mm.); and with five specimens of _R. cataractae_: KU 4248, 4258, and 4264 (55.6-65.0 mm. standard length, mean 59.5 mm.). Comparative material was taken at the same locality as KU 4253 and at nearby localities in the Rio Grande. The hybrid is intermediate in almost all of the features in which the parental species differ from each other. For six of the characters included in Table 4, the hybrid index is 49.7 per cent, when _Gila_ is assigned the value 0 (height of dorsal fin and numbers of fin rays and teeth excluded). There is no enlargement of the head in KU 4253, such as was found in _Gila orcutti_ × _Siphateles mohavensis_ (Hubbs and Miller, 1943:373), _Chrosomus erythrogaster_ × _Notropis cornutus frontalis_, and _C. erythrogaster_ × _Semotilus atromaculatus_. The height of the dorsal fin, which Hubbs and Miller (_loc. cit._) found to be extreme in _G. orcutti_ × _S. mohavensis_, exceeds the average for the parental species in _G. nigrescens_ × _R. cataractae_ also; but, dorsal fins as high as that of the hybrid were found in some individuals of both parental species. In _R. cataractae_, all fins are more rounded and more expansive than in _G. nigrescens_, and fins other than the dorsal have an intermediate size in the hybrid. This intermediacy has doubtful significance, because fin-size in _Rhinichthys_ varies greatly with body-size, sex, and probably with the state of sexual development. _Rhinichthys_ matures at smaller size than _Gila_, and never becomes so large as that species.