FOSSIL REPTILES. 265 



and complete, and does not make a body with the plates of 

 the buckler which follow that of the eleventh vertebra. 



The vertebrae of the tail are free like those of the neck. 



The sea-tortoises have three longitudinal plates after the 

 tenth ; thirteen in all. But as the second and ninth are some- 

 times divided, we may reckon them fifteen. Fourteen have 

 been found in the emys serrata. The eleventh and twelfth, 

 however, are very small. There are but eleven in the land- 

 tortoises and chelydes. 



The ribs do not always catch in their entire length. To- 

 wards their exterior a narrow portion remains^ and the inter- 

 vals between it and those of the anterior and posterior ribs 

 are filled only by a cartilaginous membrane. In the fresh- 

 water tortoises and chelydes, this buckler is entirely filled up 

 in course of time, and the ribs catch, in their whole length, 

 both with each other and the marginal pieces. Ossification 

 goes on still more rapidly in the land-tortoises ; and it is only 

 in their early age that vacancies are observable between the 

 external parts of their ribs. This buckler is, more or less, 

 gibbous, according to the species. There are many other 

 variations which our plan and limits oblige us reluctantly to 

 pass unnoticed. 



The sternum, or anterior portion of the buckler, is composed 

 of nine pieces ; the atlas of four. The axis and the succeed- 

 ing vertebrae are composed of a body nearly rectangular, cari- 

 nated underneath, concave in front, convex behind, and of 

 an annular part which remains distinct from the body during 

 life, by two sutures, is raised above by a crest, instead of a 

 spinous apophysis ; and its anterior articular apophyses, 

 placed at first under the posterior apophyses of the preced- 

 ing vertebrae, rise obliquely to embrace them, as far as the 

 sixth, and resume a little their horizontal position in the two 

 following. 



The bone which proceeds from the dorsal buckler to the 



sternum is suspended by a ligament under the dilatation of 



