_Geographic variation._--_T. spinifer_ is the most variable and widespread species of the genus in North America. Size of ocelli on the carapace decreases from east to west on turtles inhabiting waterways of the Upper Mississippi River drainage. The most impressive gradient, geographically oriented from western Louisiana to southwestern Texas is seen in each of several features: decrease in size of tubercles on the anterior edge of the carapace, reduction in contrast of pattern on the dorsal surface of limbs and side of head, change in pattern on the dorsal surface of the snout, and increase in the size of white spots on the carapace. But the gradient in size of white spots is reversed in _T. s. emoryi_, which has small white spots on the carapace. Some of the characters at the western terminus of this geographical gradient are shared with _T. ater_ and _muticus_. Those subspecies comprising the _emoryi_ group also show proportional characters that correspond closely with those of _T. ferox_. On the basis of tuberculation and pattern on carapace, side of head, dorsal surface of limbs and snout, _Trionyx spinifer_ may be divided into six subspecies. =Trionyx spinifer spinifer= Lesueur Eastern Spiny Softshell Plates 33, 34, and 52 _Trionyx spiniferus_ Lesueur, Mém. Mus. Hist. Nat. Paris, 15:258, pl. 6, December, 1827. _T[rionyx] s[pinifer] spinifer_ Schwartz, Charleston Mus. Leaflet, No. 26:11, May, 1956. _Trionyx ocellatus_ Lesueur, Mém. Mus. Hist. Nat. Paris, 15:261, December, 1827. _Apalone hudsonica_ Rafinesque, Atlan. Jour., Friend Knowledge, Philadelphia, 1(No. 2, Art. 12):64, Summer, 1832. _Trionyx annulifer_ Wied-Neuwied, Riese Nord-Amerika, 1(pt. 3):140, 1838. _Tyrse argus_ Gray, Cat. Tort. Croc. Amphis. Brit. Mus., p. 48, 1844. _Aspidonectes nuchalis_ Agassiz, Contr. Nat. Hist. United States, 1(pt. 2):406, 1857. _?G[ymnopus] olivaceus_ Wied-Neuwied, Nova Acta Acad. Leopold.-Carol., 32:55, pl. 5, 1865. _Type._--Lectotype, Museum d'Histoire Naturelle, Paris, No. 8808; large stuffed female obtained by C. A. Lesueur from the Wabash River, New Harmony, Posey County, Indiana (Pl. 52). _Range._--Northeastern United States and extreme southeastern Canada in tributaries flowing into the Mississippi River from the east, and the St. Lawrence River drainage; extreme southern Quebec and Ontario, Canada, east through southern Great Lakes region to Wisconsin, and south through New York, western Pennsylvania and Illinois to Tennessee and western Virginia (see map, Fig. 19). _Diagnosis._--Juvenal pattern of large, thick-bordered black ocelli, often 9-10 millimeters in diameter in center of carapace on adult males, and 2-3 millimeters in diameter on hatchlings (mean OD/PL, Michigan, .066); only one dark marginal line separating pale rim of carapace from dorsal ground color.