The occurrence of the two clines, _spinifer-hartwegi_ and _pallidus-guadalupensis_, in the species _spinifer_ are notable in that the former occurs mostly in one large continuous drainage system, that of the Mississippi, and shows no sharp break in the one character distinguishing the two subspecies whereas populations composing the _pallidus-guadalupensis_ cline are separated into several river drainages, and show a relatively sharp break in several characters at the Brazos-Colorado river divide. This situation seemingly supports the thesis that clines are maintained by some sort of parallel gradient in ecological or geological conditions. It is notable that streams draining the Edward's Plateau (inhabited by _guadalupensis_) differ in quantity (more) and quality (especially CO_{3}^{--}, Ca^{++}, and Mg^{++} ions) of their solutes, and probably pH (higher) from those farther east (Hubbs, 1957:102). The gross difference in habitats mentioned above (sandy, turbid, sluggish streams in the west _vs._ clear, swift streams in the east) may affect the differentiation recognizable in the _spinifer-hartwegi_ cline. Daily and Seasonal Activity _Diurnal Habits_ Softshells bask on débris in the water or on banks close to the water; basking presumably raises the bodily temperature. In general in the southeastern and southwestern United States, I have seen softshells basking only rarely but once saw six at one time close together on logs in Bowie Creek, Hattiesburg, Mississippi (species undetermined). Surface (1908:122) saw _spinifer_ in rows on rocks or logs in tributaries of the Ohio River. Duellman and Schwartz (1958:271-72) stated that _ferox_ basks on banks or beds of aquatic vegetation. Deckert (1918:31) mentioned large _ferox_ "sunning in shallow water at edge of pond." Minton (1944:447) wrote that _muticus_ and _spinifer_ sun on steep mud banks (Wabash River). Cahn (1937:180) stated that _muticus_ (in Illinois) basks on banks at the water's edge but seldom on logs, and suggests that _muticus_ is less prone to leave the water than _spinifer_. According to Carr (1952:438), _muticus_ never basks on logs or rocks. In Ohio, Conant (1951:159) mentioned _spinifer_ as occasionally basking upon a log or rock, or sometimes on steep clay banks of streams. On banks, quick escape is facilitated by directing the head toward the water, thus eliminating the time that it would take to turn around on land (Conant, _loc. cit._; Newman, 1906:129). Evermann and Clark (1920:593) mentioned _spinifer_ as basking on sandy or grassy shores, and large boulders. Muller (1921:181) wrote that _muticus_ basks four to ten feet from the water's edge on gently sloping sand and mud shores of small islands in the Mississippi River (near Fairport, Iowa). Muller stated that basking usually occurs in the morning, up until 2 p. m., and that beaches with a northern exposure were preferred; he observed 37 turtles within a 50-foot stretch of beach. In captivity,