22 CHELONURASERPENTINA. 



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



Chelydra serpentina, Fit:., Neue, Class, der Rept, p. 45. 



Chelydra serpentina, TViigler, Natur. Syst. der Amph., p. 136. 



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



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



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



Emysaurus serpentina, Dmn. et Bih., Hist. Nat. des Rept, torn. ii. p. 350. 



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



Description. The shell is subquadrilateral, smaller and entire in front, larger 

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

 gonal, 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 fourth, and broader behind, where 

 it is joined to four marginal plates, with a prolonged angle that runs in between 

 the supra-caudals: superiorly the shell along the vertebral line is so flat that 

 these plates are situated nearly on a horizontal plane, the anterior dipping 

 almost imperceptibly forwards, and the posterior dipping a little more downw^ards 

 and backwards. The anterior lateral plate is irregularly triangular, with its 

 external border rounded and joined to five marginals, and its internal straight 

 where it joins the second, and concave where it is united to the third vertebral 

 plate; the second and third laterals 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 is surrounded with a prominent knob or 

 tubercle; those of the vertebral range are placed at the centre of the posterior 



