312 FOSSIL REPTILES. 



the first of the back. Their body is more long than broad, 

 and more broad than high. The faces are of a transverse 

 oval form^ or kidney-shaped. Others are minus of the lower 

 apophysis, but in all the rest resemble the preceding. These 

 are the middle dorsal. Some follow which have no articular 

 apophyses : these are the last dorsal, the lumbar, and the first 

 caudal. Their peculiar place is recognized by their transverse 

 apophyses, which are elongated and flattened more and more. 

 The articulary faces of their body are nearly triangular in the 

 first caudal. Those which follow have, beside their upper spinous 

 apophysis and the two transverse, two little facets at their 

 lower face, to support the chevron-formed bone. The articular 

 faces of their bodies are pentagonal. Then come some more 

 which do not differ from the preceding, but by the want of 

 transverse apophyses. They form a large portion of the tail, 

 and the faces of their body are ellipses, at first transverse, and 

 then more and more compressed at the sides. The chevron- 

 formed bone is not articulated, but soldered, and forms a body 

 with them. 



Finally, come the last vertebrae of the tail, which have no 

 apophyses whatever. In proportion as they approach the end 

 of the tail the bodies of the vertebrae are shortened, and almost 

 from its commencement they have less length than breadth 

 and elevation. The length ends by being one half less than 

 the height. 



This series of vertebrae gives rise to many important remarks. 

 The first is relative to the chevron-formed or rafter bone, and 

 the position of its articulation. Its length, and that of the 

 spinous apophysis opposed to it, prove that the tail was very 

 much raised vertically. The absence of transverse apophyses 

 on a great portion of the length of the tail, proves at the same 

 time that it was very much flatted at the sides. The animal 

 was therefore aquatic, and swam after the manner of the cro- 

 codiles, causing the oar of its tail to act right and left, and 

 not up and down like the cetacea. The monitors have the 



