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... , ~ , ~. <br />.. <br />.. . <br />96 <br />Gila emoryi, Baird and Girard, 18536: 338. Jordan and Gilbert, 1883: 229. <br />Gila emorii, Girard, 1856: 205/ 1859a: 62. Cope and Yarrow, 1875: 667. <br />Jordan and Gilbert, 1883: 241. Kirsch, 1889: 558. <br />Gilo elegans, Girard, 1856: 205/ 1858: 286/ 1859a: 61. Jordan and Gilbert, <br />1883: 227. Jordan, 1885: 818/ 18916: 22. Evermann and Rutter, 1895: 482. Jor- <br />dan and Evermann, 1896: 226. Gilbert and Scofield, 1898: 492. Meek, 1904: <br />xxxix, 53. Snyder, 1915; 580. Jordan et al., 1930: 114. Evermann and <br />Clark, 1931: 62. Moffett, 1942: 82/ 1943: 182. Dill, 1944: 153. Rostland, 1952: <br />270. Minckley and Alger, 1968: 94. Minckley and Deacon, 1968: 1427. Vanicek <br />• and Kramer, 1969: 193. Rinne and Minckley, 1970: 18. Holden and Stalnaker, <br />1970: 409. Minckley, 1971: 185. <br />Gila robusta elegans, Miller, 1945c: 104/ 1946c: 410/ 1955: 131 / 1961 a: <br />544/ ]9616: 373/ 1963a: 1. Wallis, 1951: 90. LaRivers, 1952: 101. 1962: 391. <br />LaRivers and Trelease, 1952: 116. Shapovalov, et al., 1959: 172. Miller and Hubbs, <br />1960: 31. Follett, 1961; 216. Miller and Lowe, 1964:.140/ 1967: 104. Uyeno and <br />Miller, 1965: 39. Cole, 1968: 471. <br />Body highly streamlined; skull concave on dorsum, arching smoothly into a <br />predorsal hump in adults. Total vertebrae (including urostyle and four vertebrae <br />modified into Weberian appartus), 47 to 50. Caudal peduncle thin, pencil-like, its <br />length divided by length of head 1.0 or more; length of head divided by depth of <br />caudal peduncle usually 5.0 or more. Squamation sometimes incomplete, with <br />scales absent or highly embedded on predorsum, venter, or caudal peduncle <br />(usually fully scaled). Fins large, falcate, with origin of dorsal nearer tip of snout <br />than to caudal-fin base. Dorsal fin-rays almost always 10 or more; anal fin-rays <br />usually T0. Mouth terminal and somewhat oblique. Dorsal and ventral rami of <br />pharyngeal arches about equal in length, teeth 2, 5-4, 2. <br />Color dark above and light below, very dark (almost black) when from clear <br />waters, or pallid when from turbid streams. Fins often dusky, with yellow pigment <br />- near bases (especially of paired fins). <br />This unique species now appears extinct in the moderate-sized <br />tributaries of the Colorado River, such as the Gila and Little Colorado. It <br />was described from specimens reportedly taken from the now-dry Zuni <br />River in New Mexico (Baird & Girard, 1853a, c}. The fish persists in <br />unknown numbers in some mainstream reservoirs of the Colorado River, <br />and maintains an apparently-declining population in the Colorado River <br />upstream from Grand Canyon. <br />Gila elegans, and the bizarre humpback chub discussed next, exhibit <br />some of the most unique morphological adaptations to the constant <br />stress of current that are known in fishes: <br />"In more obvious adaptation (the fishes) .tend to be larger <br />and much more stream-lined with more terete bodies, sharper <br />entering wedges, and, particularly, with much slenderer caudal peduncles <br />and longer and more falcate fins; and often with more rays in one or <br />more fins or with smaller scales (Hubbs, 1941] .. . <br />1 <br />S <br />The smaller, reduced or embedded scales and relatively smaller <br />eyes of these fishes may be adaptations to the high silt loads which <br />'' j characterized the remarkably-erosive, turbid Colorado River system prior <br />! to construction of dams. Fishes in other swift rivers and streams often <br />4 <br />