Occasional specimens have only one definite dark line paralleling the rear margin of the carapace. Schwartz (1956:16) reported that Charleston Museum No. 55.159.26 has only one solid line at the margin of the carapace, and I received an adult male (KU 47120) reported to have come from the Pearl River that is aberrant in not having more than one dark marginal line. USNM 95191, a large stuffed female from the Pearl River is mentioned by Stejneger (1944:59, Pl. 17) as having marks that "assume the form of short lines parallel with the submarginal ring"; I examined this specimen and noted that it had only one dark marginal line. Stejneger (_op. cit._:64) mentioned another from the Pearl River drainage, and Crenshaw and Hopkins (1955:20) wrote that some individuals from Georgia have only one dark marginal line. Presumably MCZ 1606 (now in the Albany Museum) recorded by Stejneger (_op. cit._:52) as _Amyda s. spinifer_ from Columbus, Georgia, is another specimen. [Illustration: FIG. 21. Basicranial length and greatest width of alveolar surface of maxilla on 52 skulls of _T. spinifer_ (open circles) and 11 of the _agassizi_-form (solid circles; half shaded circle represents holotype of _agassizi_). Most skulls of the _agassizi_-form that exceed 43 mm. in basicranial length have a more expanded, alveolar surface of the maxilla than skulls of _spinifer_ of approximately the same size. All skulls exceeding 50 mm. are those of females.]