55 



EMYS CUMBERLANDENSIS. 



Piatt VIII. 



Characters. Head of moderate size; upper jaw slightly emarginate; lower 

 jaw furnished with a small hook in front; shell rubround; indistinctly carinate; 

 slightly notched anteriorly, and beautifully serrated posteriorly; sternum full, 

 entire in front, truncated behind. 



Description. The shell is much flattened and subround in form, having a dis- 

 tinct though slightly elevated carina throughout its whole extent; the anterior 

 margin is slightly notched, while its posterior is beautifully serrated. The first 

 vertebral plate is hexagonal, elevated into a small prominence at the centre of its 

 posterior part, where the carina begins; its greatest extent is in the antero-poste- 

 rior direction, with its posterior margin projecting at the centre, and its anterior 

 marked by three small articulating facets; the second vertebral plate is also hex- 

 agonal, with acute lateral angles, its anterior margin concave to receive the first 

 vertebral; its posterior straight, and with its greatest extent in the transverse di- 

 rection; the third vertebral is nearly of the same form, but has a small pike on its 

 posterior margin, to be received in the fourth vertebral plate, which is also hex- 

 agonal, but shorter, and has a notch both on its anterior and posterior margins. 

 These plates are smooth, except the first and fifth, which are marked near the 

 marginal plates with a few slight concentric stria3. The first lateral plate is nearly 

 an equilateral triangle, with its basis downwards and forwards, and joined to five 

 marginals; the second is pentagonal, with three facets on its lower and larger 

 border; the third is irregularly hexagonal, and the fourth quadrilateral. These 

 plates are also slightly marked with five or six longitudinal concentric striae near 

 their junction with the marginal plates. There are twenty-five marginal plates; 



