140 CHELONURA SERPENTINA. 



Emys serpentina, Merrem, Versuch eines Syst. der Amphib., p. 23. 



Chelonura serpentina, Say, Jour. Acad. Nat. Scien. Philad., vol. iv. p. 206-217. 



Testudo serpentina, Leconte, Ann. Lye. Nat. Hist. N. Y., vol. iii. p. 127. 



Chelydra serpentina, Fitzinger, Neue Class, der Rept., p. 45. 



Chelj'dra serpentina, JVagler, Naturlich. Syst. der Amphib., p. 1 36. 



Chelydra serpentina. Gray, Synops. Rept., p. 36. 



Chelonura serpentina, Bonaparte, Osser. Sul., 2nd ed. Reg. An., p. 174. 



Chelonura serpentina, Harlan, Med. and Phys. Res., p. 157. 



Emysaurus serpentinus, Dumeril et Bibron, Hist. Nat. des Rept., torn. ii. p. 350. 



Snapping Turtle, Vulgo, or Alligator Couta, or Cooler, by the negroes. 



Description. The shell is sub-quadrilateral, smaller and entire in front, 

 larger behind, and deeply emarginate and serrate. The first vertebral plate is 

 octagonal, broadest in the transverse direction, pointed anteriorly, and passes into 

 the nuchal, or intermediate, marginal plate, and is slightly notched posteriorly for 

 receiving the second vertebral, which is nearly quadrilateral, with a point in the 

 centre of its anterior margin and a minute notch on its posterior that fits it to the 

 adjoining plate; the third vertebral is also nearly quadrilateral, with its posterior 

 border slightly concave; the fourth is octagonal, with its two anterior margins 

 meeting at an obtuse angle in front, while its posterior border presents a slight 

 concavity for the fifth vertebral plate, which is urceolate and irregularly octagonal, 

 narrow^ in front, and passing into the foiu'th, and broader behind, where it is joined 

 to four marginal plates, with a prolonged angle that runs in between the supra- 

 caudal: superiorly the shell along the vertebral line is so flat that these plates are 

 situated nearly on an horizontal plane, the anterior dipping almost imperceptibly 

 forwards, and the posterior dipping a little more downwards and backwards. 

 The first lateral plate is irregularly triangular, with is external border rounded 

 and joined to five marginal, and its internal straight where it joins the second, and 

 concave where it is united to the third vertebral plate; the second and third 

 lateral are very regularly quadrilateral, each with an indistinct point that runs up 

 between two adjoining vertebral plates, and each with three articulating facets 

 below; the fourth is very irregularly quadrilateral, narrow above and broad below, 

 with three facets, and its inferior anterior angle prolonged: each of these plates 



