24 KINOSTERNONPENNSYLVANICUM. 



Cistuda pennsylvanica, Say, Jour. Acad. Nat. Scien. Philad., vol. iv. p. 216. 



Testudo pennsylvanica, Leconte, Ann. Lye. Nat. Hist. N. Y., vol. iii. p. 120. 



Kinosternon pennsylvanicum, Bell, Zool. Jour., vol. ii. p. 304. 



Kinosternon pennsylvanicum, Gray, Synop. Rept, p. 33. 



Cinosternon pennsylvanicum, Wag., Naturlich. Syst. der Amph., p. 137. 



Emys pennsylvanica, Harl., Med. and Phys. Res., p. 155. 



Mud tortoise, Vulgo. 



Description. The shell is oval, gibbous, though a little flattened along the 

 vertebral line, with an entire or slightly notched margin posteriorly. There are 

 five very large vertebral plates; the anterior is long, nari'ow and triangular, with 

 its basis forward, and its apex truncate and directed backwards, and having a 

 slight prominence in the middle; the second, third and fourth are hexagonal, with 

 their anterior angles rounded and their lateral angles acuminate; the fifth is 

 irregularly quadrilateral, smaller above and larger below, where it joins four 

 marginal plates: all these vertebral plates are more or less imbricate posteriorly. 

 Of the lateral plates, the anterior is irregularly quadrilateral; the second and third 

 are pentagonal and acuminate where they join the vertebral plates; the fourth is 

 pentagonal. The marginal plates are twenty-three in number; the nuchal or 

 intermediate is an oblong square, small and narrow; the first, second and third 

 are quadrilateral, narrow and elongated; the remaining marginal plates are quadri- 

 lateral and broader; the tenth with unequal margins. 



The sternum is shorter than the carapace; it is oval, rounded, and full in front, 

 and emarginate behind. The gular plates are consolidated to form a single plate, 

 which is triangular, with its apex posterior; the brachial are quadrilateral; the 

 thoracic are triangular, with their apices turned inwards: these five plates are all 

 united firmly together and form the anterior section of the sternum, which is so 

 joined by ligamento-elastic tissue to the abdominal plates as to form a hinge joint. 

 The abdominal plates are large, quadrilateral, and fixed to the shell; the femoral 

 are triangular and the subcaudal are quadrilateral: these four latter plates are 

 united to each other and form the posterior section of the sternum, and are joined 

 to the posterior border of the abdominal plates by a ligamento-elastic tissue, 



