Specimens were obtained from the following institutions: University of Alberta (abbreviated UA in the text); Museum of Zoology, University of Michigan (UMMZ); University of Missouri (UM); Montana State College (MSC); University of Oklahoma Museum of Zoology (UOMZ); University of Saskatchewan; Royal Ontario Museum, Division of Zoology, Toronto (ROMZ); University of Wyoming (WU); Museum of Natural History, University of Kansas (KU). Specimens examined are listed in the accounts of the subspecies.
We are grateful to D. A. Boag, Reeve M. Bailey, Arthur L. Witt, C. J. D. Brown, Carl Riggs, F. M. Atton, W. B. Scott, and George Baxter, all staff-members of the institutions listed in the immediately preceding paragraph, for placing specimens at our disposal. Mr. William Peters analyzed the contents of stomachs of specimens that were used for study of the food habits. Mr. Artie L. Metcalf assisted in collecting specimens. Drs. Kenneth B. Armitage and E. Raymond Hall offered valued suggestions in connection with the preparation of the manuscript.
_Description._--Pharyngeal teeth 2,4-4,2, hooked; dorsal fin of moderate size, falcate, first principal ray longest, extending beyond posterior rays in depressed fin, its origin usually slightly in front of insertion of pelvic fin, approximately equidistant from tip of snout and base of caudal fin, rays 8, rarely 9; pectoral fin strongly falcate, rays 14-20, usually 16-18; pelvic rays 8, rarely 9; anal fin falcate, rays 8, rarely 9; caudal rays 19, rarely 20.
Body slightly compressed, nearly terete; head-length 23.1-28.8 per cent of standard length; head broad and flattened, snout subconical, premaxillae protractile, upper lip not medially expanded; mouth subterminal, nearly horizontal, large; a single pair of terminal maxillary barbels; orbit usually 5-7 per cent of standard length; lateral line slightly decurved; intestine short, peritoneum silvery.
Color brown or olivaceous dorsally, silver or creamy white ventrally, without distinctive markings; dusky lateral band evident in preserved specimens.
Taste-buds present on membrane between first and second principal rays of all fins, and on first to sixth interradial membranes of pectoral fin. On the caudal fin, taste buds between first and second principal rays of upper and lower lobes, though present, are less well developed than on other fins. Moore (1950:88) states that taste buds are numerous on the barbels, cheeks, lips, chin, snout, opercles and branchial membranes, and are present in decreasing numbers over the body.