GILBERT: FISHES OF THE SUBGENUS LUXILUS Fenneman, Nevin M. 1938. Physiography of eastern United States. McGraw-Hill Book Co., New York, v-xiii + 714 pp. and 196 figs. Flint, Richard Foster 1947. Glacial geology and the Pleistocene Epoch. John Wiley and Sons, New York, 589 pp., 88 figs., 30 tables, 6 pls. 1957. Glacial and Pleistocene geology. John Wiley and Sons, New York, v-xiii + 553 pp., many figs. and tables, 5 pls. Forbes, Stephen A. 1909. On the general and interior distribution of Illinois fishes. Bull. Illinois St. Lab. Nat. Hist., 8: 381-437, maps 1-103. Forbes, Stephen A., and Robert E. Richardson 1920. The fishes of Illinois. Second edition. Ill. St. Jour. Co., Springfield, vol. 3, cxxxi + 357 pp., many figs. and color pls., separate vol. of 103 maps. Fowler, Henry W. 1904. Notes on fishes from Arkansas, Indian Territory and Texas. Proc. Acad. Nat. Sci. Phila., 56: 242-249, 1 fig. 1909. A synopsis of the Cyprinidae of Pennsylvania. Proc. Acad. Nat. Sci. Phila. (1908), 60: 517-553. 1910. Notes on the variation of some species of the genus Notropis. Proc. Acad. Nat. Sci. Phila., 62: 273-293, pls. 15-21. 1922. Records of fishes for the southern and eastern United States. Proc. Acad. Nat. Sci. Phila., 74: 1-27, 2 pls. 1923. Records of fishes for the southern states. Proc. Biol. Soc. Wash., 36: 7-34. 1936. Fresh-water fishes obtained in North Carolina in 1930 and 1934. Fish Culturist, 15(10): 192-194. 1945. A study of the fishes of the southern Piedmont and coastal plain. Monog. Acad. Nat. Sci. Phila., 7: i-vi, 1-408, figs. 1-313. Gibbs, Robert H., Jr. 1957. Cyprinid fishes of the subgenus Cyprinella of Notropis. I. Systematic status of the subgenus Cyprinella, with a key to the species exclusive of the lutrensis-ornatus complex. Copeia, 1957(3): 185-195. Gilbert, Carter Rowell 1961a. A systematic and geographical study of the subgenus Luxilus (family Cyprinidae). Dissertation Abstracts, 21(8): 2411-2412. 1961b. Hybridization versus intergradation: an inquiry into the relationship of two cyprinid fishes. Copeia, 1961(2): 181-192. Gilbert, Charles H. 1884a. Notes on the fishes of Kansas. Bull. Washburn Coll. Lab. Nat. Hist., 1(1): 10-16. 1964