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Stanton's Cave is 51 river kilometers below Lees Ferry, Coconino County, Arizona, in the inner gorge of Mar- ble Canyon, and lies at an elevation of 927 meters. Here the river makes an abrupt S-bend some 50 river kilo- meters north of the mouth of the Little Colorado River. The entrance to the cave lies 44 meters above the river and measures about 6.1 meters wide and 9.1 meters high; passageways extend almost 61 meters into the limestone bluff. The site is designated Ariz. C:5:3 in the archeological survey records of Grand Canyon National Park. The fish remains recovered from Stanton's Cave by Robert C. Euler (Table 5-1) represent nearly all of the species known to be native to this part of the Colo- rado River: the humpback chub, Gila cypha Miller; bonytail, Gila elegans Baird and Girard; and Colorado-} squawfish, PVhocheilus lucius Girard, orinidae (minnows); the flannelmouth sucker, Catostomus lati- pinnis Baird and Girard, and bluehead sucker, Catos- tomus discobolus Cope, of the Catostomidae (suckers). Among the large riverine fishes, only the razorback sucker, Xyrauchen texanus (Abbott), is missing. The roundtail chub, Gila robusta Baird and Girard, is rare in the main river, but does occur in the Little Colorado River. The only mainstream records are from near and well above Lees Ferry (Holden and Minckley 1980). Notes on Gila cypha, Humpback chub Bones of the humpback chub in Stantoes Cave pro- vide evidence for the ancient distinctiveness of this species. This large, bizarre minnow is known to attain a maximum size of 320 mm S.L. Its type locality is in Grand Canyon near the mouth of Bright Angel Creek (Miller 1946). It has since been recorded as far down- river as Boulder Canyon, 39 km below Hoover Dam (from archeological material, Miller 1955), and as far up the Colorado River drainage as Flaming Gorge and Hideout Canyon on the Green River, to just north of the Wyoming border (Smith et al. 1979). We may spec- ulate that it once occurred up, the San Juan giver at least as far as the Goosenecks, which begin a few kilo- meters west of Mexican Hat, Utah. The humpback chub is now known to be present in the Colorado drainage at (1) the canyon region of the lower Yampa and Green rivers in Dinosaur National Monument, (2) Desolation and Gray canyons in the lower Green River, (3) the Black Rocks area in Ruby Canyon, and Westwater Canyon, both on the Colorado River not far above and below the Utah-Colorado state line, and (4) the Grand Canyon region, chiefly the lower 21 km of the Little Colorado River (Behnke and Benson, 1980, and supplementary information). The controversy over the recognition of the hump- back chub as a full species (Miller 1955; Minckley and Deacon 1968; Holden and Stalnaker 1970) has been dis- cussed by Smith et al. 1979, who dealt with morpho- metric and meristic traits. One potentially valuable organ system, the skeleton, has heretofore remained almost unexplored for systematic characters that might help to resolve the uncertainty over recognizing the humpback chub as a full species. Because the Stanton's Cave material co nnrisec bones only we have exan1- ined the skeletons of big-river members of the genus Gila that inhabit the middle and upper parts of the Col- orado River basin: Gila robusta, G. elegans, and G. cypha. Our observations are summarized below. The cave material (Table 5-1) is from: (1) the surface of antechamber 1 (June 17, 1969, R.C. Euler, J. Ware, B. Harrill, collectors), an incomplete neurocranium with Weberian apparatus attached (Figure 5-11)), plus 9 attached vertebrae and 3 ribs; and (2) a pack rat's nest adjacent to FS #14 (June 1969,"L. Powers, collector), a left pectoral girdle (Figure 5-3B). All of these remains are non-mineralized; their age may be as great as 4000 years B.P.(Robert C. Euler, personal communication, 1971). One of the best osteological features that distinguish Gila cypha from its relatives is the prominent supra- occipital process (Figure 5-1C,D), which is expanded so that the dorsal border lies above the dorsal profile of the skull (consistent in 5 skulls examined). This enlarged process, evidently developed for muscle attach- ment associated with the prominent fleshy hump, is also readily seen on radiographs (58 examined, repre- senting materials from widely separated localities) where it is well developed in specimens that have attained 200 mm S.L. In Gila robusta (Figure 5-1A) the process is elongate but not elevated, and in G. elegans (Figure 54B) it is higher than in robusta but does not extend above the dorsal profile of the skull. The angle of the neural and hemal spines to the cen- tre of the posterior caudal vertebrae is a useful feature used to separate Gila cypha and its close relatives (Gehl- bach and Miller 1961; Minckley and Alger 1968). The vertebral spines of G. robusta are least parallel and those of G. elegans are most parallel with the centra (Figure 5-2A-D). The anterior arm of the pectoral girdle is distinctive in Gila cypha. A strong dorso-lateral ridge forms a deep sulcus at the base of the posterior (vertical) arm, where- as in both G. elegans and G. robusta this ridge is weak or obsolete (Figure 5-3A,B). in a m en?a? y, I- Specie recovered i- m Stanton Cave include, among the minnows (family Cyprinidae), Gila cypha, humpback chub, with a weight to nearly 1 kg, locally common; Gila elegans, bonytail, with a weight to nearly 1 kg, rare; and PVhocheilus lucius, Col- orado squawfish, with a weight to over 20 kg, rare. Among the suckers (family Catostomidae) are Catos- tomus latipinnis, flannelmouth sucker, with a weight to over 1 kg, locally common; and Catostomus discobolus, bluehead sucker, with a weight to ca. 5 kg, locally common. Acknowledgments We are grateful to Ted Hatch, of Hatch River Expe- ditions, for facilitating our river survey in 1968 from Lees Ferry to Diamond Creek. In 1975, the first author was sponsored for a similar trip by the National Park Service. In both years, permits to collect were kindly arranged by the Arizona Game and Fish Department and the Superintendent of Grand Canyon National Park. Michael L. Smith determined several of the sucker bones. We thank George Junne for preparing Figures 5-1-3. To Frances H. Miller we are indebted for typing and editing the manuscript. 61