Reptiles and Amphibians of Illinois. 219 



7 (8). Plastron truncate before and behind. Alveolar sur- 

 faces of jaws moderately narrow. Digits short. 



Chrtsemts. 



8(7). Plastron distinctly emarginate behind. Alveolar sur- 

 faces of jaws wider. Digits longer than in Chrysemys. 



PSEUDEMTS. 



9 (5). Plastron deeply emarginate behind, slightly before. 

 Digits long and fully webbed Malacoclemmts. 



OlSTUDO, Flemin-g. 



Fleming, Philosophy of Zoology, 1822, p. 270. 

 Hoffmann, Bronn's Thier Keich, Reptilien, p. 378. 



Carapace strongly convex or hemispherical. Plastron 

 large, rounded before and behind, capable of completely clos- 

 ing the carapace, and affixed to the latter by a ligamentous 

 articulation; a transverse movable hinge between the pectoral 

 and abdominal plates, these plates with no wings in adults. 

 Axillary and inguinal plates small or wanting. Digits 5-4 or 

 5-3, only the terminal phalanges free, with small interdigital 

 webs. 



Oistudo Carolina, Linn. Box Turtle. 

 Var. Carolina. 



Testudo earoUna, Linn., Syst. Nat., ed. 10, 1758, 1., p. 198.— LeC, 



Ann. Lye. Kat. Hist. N. Y., 1829, III., p. 97. 

 Cistudo Carolina, Dum. et Bibr., Erp. Gen., II., 1835, p. 210.— 



Holbr., N. A. Herp., 1842, 1., p. 31. pi. 2.— De Kay, Nat. Hist. 



N. Y., I., Zool. III., Rept. and Amph., 1842, p. 24, pi. 1, fig. 



1.— Gray, Cat. Tortoises, etc., in Coll. Brit. Mus., 1844, p. 30. 

 Cistudo dausa, subsp. cJausa, Davis and Rice, Bull. 111. State 



Lab. Nat. Hist., I., No. 5, 1883, p. 57. 

 Cistudo clausa, Davis and Rice, Bull. Chicago Acad. Sci., 1883. 

 ^ Var. triunguis. 



Cistudo triunguis, Ag., L., Contr. Nat. Hist. U. S., 1857, 1., p. 445. 

 Cistudo dausa, subsp. triunguis, Davis and Rice, Bull. 111. State 



Lab. Nat. Hist., I., No. 5, 1883, p. 57. 



Length of shell about six inches; carapace strongly con- 

 vex, highest before the middle. Nuchal plate very small, 

 slightly projecting; anterior and posterior marginals slightly 

 flared outwards. Caudals directed downwards. Two gular 



