Color notes taken from a freshly-killed adult male (KU 47121) from the Brazos River, seven miles below Whitney Dam, Bosque-Hill county line, Texas, are: Carapace pale brown or tan bordered by black line, having pale lemon yellow rim; yellowish-cream spots on carapace faintly surrounded with black stippling; dorsal surface of soft parts of body olive having black marks and patches of grayish; webbing on limbs having golden or yellowish hue, brighter distally; interorbital region brown; black-bordered, postocular stripe orange-cream; snout and side of head olive having pale areas of orange-cream; iris cream having black stripe; yellowish at juncture of dark dorsal and pale ventral coloration with orangish tinge on forelimbs and head; tail pale brown or tan, flanked by black borders that suffuse laterally into lemon-yellow; undersurface whitish, pale yellow on neck, bluish-gray on throat.
Comparisons.—T. s. pallidus most closely resembles T. s. guadalupensis, but can be distinguished from that subspecies in having small white tubercles, rarely two millimeters in diameter, on a pale background, that are not surrounded by blackish ocelli, and are usually absent, or not conspicuous on the anterior third of the carapace in adult males; also there are usually no conspicuous white tubercles or dots on the anterior third of the carapace in hatchlings. Many adult males of pallidus from the Brazos and some from the Trinity River drainages often have dusky or black ocelli surrounding the white dots posteriorly on the carapace; males from these river systems may be distinguished from guadalupensis in having most, if not all, white dots on the anterior half of the carapace smaller than those posteriorly, and a pale brown carapace (in life, usually darker in guadalupensis). T. s. pallidus (and guadalupensis) is distinguished from emoryi in lacking a widened pale rim posteriorly, and in having small white spots on the anterior half of the carapace. T. s. pallidus resembles guadalupensis and emoryi in having white spots on the carapace in adult males. T. s. pallidus differs from spinifer, hartwegi and asper in lacking blackish dots or ocelli that occur in the center of [526] the carapace. T. s. pallidus resembles emoryi but differs from guadalupensis in lacking black ocelli surrounding the white spots. T. s. pallidus resembles spinifer, hartwegi and asper but differs from guadalupensis and emoryi in having tubercles along the anterior edge of the carapace that are conical having sharp tips in males, and conical in large females.
T. s. pallidus resembles spinifer and hartwegi but differs from the other subspecies in having a narrow head. T. s. pallidus differs from emoryi but resembles the other subspecies in having a wider carapace. T. s. pallidus resembles emoryi and guadalupensis, and differs from the other subspecies in having the carapace widest farther posterior than one-half the length of the carapace. The snout of pallidus and guadalupensis is shorter than in spinifer and hartwegi, but longer than in emoryi. T. s. pallidus differs from asper but resembles the other subspecies in having a relatively long plastron.
Remarks.—Intergradation of the subspecies pallidus and guadalupensis is of a clinal nature in which populations successively show a gradual resemblance to guadalupensis from western Louisiana and eastern Texas westward to central Texas. Because the sharpest break in this cline of characters occurs between the Colorado and Brazos River drainages, the turtles living in the Brazos River drainage and eastward are referred to pallidus, whereas those in the Colorado River drainage and westward are referred to guadalupensis. For further comments on intergradation between these two subspecies, see the account of T. s. guadalupensis.
Taylor (1935:217-18) reported on some specimens of Amyda spinifera that were obtained by Mr. R. E. McEntyre in "… the spring and summer of 1926, chiefly about Lewisville, Lafayette County (Arkansas)." Of the catalog numbers listed by Taylor from Lewisville, 58 (KU, alcoholic) represent pallidus. Three, having the same locality data, have features that are characteristic of hartwegi. KU 2944 (one of three specimens having this catalog number) is a female having a pale, mottled and blotched carapace approximately one foot in length; there are remnants of two dark ocelli, and many widely-scattered, well-defined dark spots near the periphery of the carapace. KU 2963 (one of three specimens having this catalog number) is an adult male that has solid, blackish dots on the entire surface of the carapace. KU 2964 (one of two specimens with this catalog number) is an adult male that has ocelli approximately five millimeters in diameter on the carapace (indistinct in center of carapace).
Lewisville is situated in the drainage basin of the Red River and is approximately eight miles east of the Red River and 30 miles west of the westernmost tributary of the Ouachita River drainage. T. s. pallidus occurs in the Red River drainage; hartwegi occurs in the Ouachita River drainage. Perhaps there is intergradation between pallidus and hartwegi in the intervening streams. There is no data to indicate from which river or stream each specimen obtained by McEntyre came; one would presume that all specimens came from the Red River drainage. But this is not certain. Certainly the 47 specimens designated herein as pallidus came from the Red River drainage. I suspect that KU 2944, 2963 and 2964 were obtained from tributaries of the Ouachita River drainage.
T. s. pallidus intergrades with the spinifer-hartwegi population where the Red River joins the Mississippi River in the lower Mississippi Valley in Louisiana. The majority of 13 juvenal specimens from the Red River near Shaw, Concordia [527] Parish, Louisiana (USNM 99862-69, 99871-75), resemble pallidus in having inconspicuous white tubercles on a pale brown carapace. The white tubercles are conspicuous in USNM 99871. Some specimens have a few small dark dots confined to the margin of the carapace, as do some "variant" individuals from well within the geographic range of pallidus. USNM 99865 is referred to hartwegi because the carapace is covered with dark ocelli approximately one millimeter in diameter. Some specimens from farther west in the Red River drainage are referred to hartwegi. One (USNM 100420) of three from Natchitoches Parish, Louisiana (TU 5763, USNM 100420-21), having blackish dots on the carapace, is applicable to hartwegi. Of two turtles from Grant Parish, Louisiana (TU 5647, 12735), only 12735 has dark dots and ocelli (hartwegi). One specimen from Rapides Parish, Louisiana (TU 14040), having dark dots on the entire surface of the carapace, is referred to hartwegi.
Most specimens from the lower Atchafalaya River drainage are referable to pallidus. Eastward, intergradation occurs with the spinifer-hartwegi population; USNM 100089-90 from Assumption Parish, near Napoleonville, Louisiana, are referred to pallidus. TU 11983, from Bayou Lafourche, Raceland, La Fourche Parish, and TU 13698.11, from Bayou Gauche in St. Charles Parish, Louisiana, are juvenal males that combine the characteristics of pallidus and hartwegi; the carapaces are covered with blackish spots and posteriorly have distinct whitish dots. The population in the Atchafalaya River more closely resembles pallidus than it does hartwegi or spinifer. In former times the Atchafalaya River was presumably continuous solely with the Red River (inhabited by pallidus). Now, these two rivers and the Mississippi River are interconnected in east-central Louisiana. A large volume of water of the Mississippi drainage is conveyed to the Gulf of Mexico by the Atchafalaya, and someone has said that by approximately 1975, unless man interferes, two-thirds to three-fourths of the total volume of water of the Mississippi River will be drained by the Atchafalaya. One can expect, therefore, an increase in the influence of the hartwegi-spinifer population in the Atchafalaya River drainage.
Specimens examined.—Total 270, as follows: Arkansas: Lafayette: KU 2930-37, 2939-40, 2942, 2944 (two of three specimens bear this catalog number), 2945-57, 2958 (2), 2959-61, 2963 (two of three specimens bear this catalog number), 2964 (one of two specimens bears this catalog number), 2965-73, 2987-89, 3056, Lewisville.
Louisiana: Acadia: USNM 100151-59, Mermentau River. Assumption: USNM 100089-90, Bayou Lafourche, "near" Napoleonville. Beauregard: TU 1231-32, 1253-55, 1291, 13211, 13266, Sabine River, 8 mi. SW Merryville. Bienville: TU 5649-50, Lake Bistineau. Caddo: TU 381, 397-99, 469-72, 474-90, 678, 10170, Caddo Lake: TU 15818-19, Cross Lake. Calcasieu: UMMZ 92754, 5 mi. W Iowa. Cameron: TU 1122, Lacassine Wildlife Refuge. Concordia: USNM 99862-64, 99866-69, 99871-75, Red River, "near" Shaw. De Soto: SM 2374-75, Wallace Bayou. Grant: TU 5647, Lake Iatt. Iberville: USNM 83985, 2 mi. E Mounds; USNM 100239-41, Grand Lake west of White Castle; USNM 100380, Plaquemine; USNM 100412, 100414-15, 100419, Spanish Lake, "near" St. Gabriel. Jefferson Davis: Calcasieu River drainage, WTN (no number, see page 524). Natchitoches: TU 5763, Bermuda; USNM 100421, "near" Natchitoches. Sabine: TU 13210, 13212-13, 13265, 13280-82, 13303-06, Sabine River, 8 mi. SW Negreet. St. Martin: USNM 100160, Bayou Chene; USNM 100650, Atchafalaya. St. Mary: USNM 100395-97, 100404, 100409-10, Berwick Bay near Morgan City.