TESTUDO. 107 



The sternum is flat, except at its union with the, carapace, in which position it is 

 convex, and anteriorly is turned upward, and has its margin angularly convex ; and 

 posteriorly it is emarginate. 



Plates of the Carapace. — (PL XXI. 1.) In the specimen there are ten vertebral 

 plates. The first is one and a half inch long, by ten lines broad. Those suc- 

 ceeding to the eighth inclusive are hexahedral ; the second to the fifth are nearly 

 equal in size ; those to the eighth successively decrease. 



The second vertebral plate articulates with the first and second pairs of costal 

 plates ; the third with the second and third ; and so on successively to the eighth 

 plate inclusive. 



The tenth vertebral plate is fourteen lines long by seventeen broad, and is divided 

 into two nearly equal triangles by the posterior border of the last vertebral scute. 



The first costal plate is three inches long by two broad, and articulates with the 

 first to the commencement of the fourth marginal plate. 



The nuchal plate is three and a quarter inches broad, and is equal to the first 

 vertebral scute. The pygal plate is twenty-two lines broad. 



Plates of the Plastron. — (PL XXI. 2.) The entosternal plate is pyriform, and is 

 two inches four lines long and broad. Its anterior extremity borders on the posi- 

 tion of the gular scutes, and posteriorly it extends to the humeral scutes. 



The anterior margin of the episternal plates is convex. Their length obliquely 

 at the middle is equal to that of the preceding plate. 



The hyosternal plates are three and a half inches long from their anterior angle, 

 and they articulate with the third to the angle of the sixth marginal plates 

 inclusive. 



The hyposternal plates are two and a half inches long at their middle, are slightly 

 oblique at the posterior margin, and articulate with the sixth and seventh marginal 

 plates. 



The xiphisternal plates include an acute notch posteriorly, and are two and a 

 quarter inches long. 



The suture between the marginal plates of the carapace and those of the plastron, 

 and the junction of the contiguous scutes from two irregular undulant intersecting 

 lines. 



Scutes of the Carapace.— {Vl. XXI. 1.) The second and third vertebral scutes 

 are nearly equal in size, each being two inches seven lines broad, the former two 

 inches long, and the latter one line longer. Their lateral margins are bow-formed, 

 and the anterior margin of the second is nearly straight, while that of the third is 

 convex forward. 



The fourth vertebral scute is slightly broader than long, being two inches two 

 lines in the former direction, and two inches one line in the latter. Its lateral 

 margins, also, are bow-formed, and converge behind, and the anterior margin is 

 angular forwards. The nuchal scute is four lines broad. 



The gular scutes together are two and a quarter wide, are convex posteriorly, 

 and do not encroach upon the position of the entosternal plate. 



Scutes of the Plastron.— (PI. XXI. 2.) The pectoral scutes are three and a 



