260 



THE BATH OOLITE PERIOD. 



CHAP. 



This vertebra has horizontal prominent ridges in the middle of 

 the sides; the articulating faces are broadly reflexed and roughly 

 bordered; the hsemapophyses separate and much reflexed on the 

 posterior edge. Neural spine broken, more than three inches wide. 



Diagram XC. Scale one-tenth of nature. 



i. Premedjal caudal vertebra, seen from below. 2. The same, seen on the left 



side. 3. The same, seen from behind. z. The zygapophysial processes. 

 h. The posterior haemapophysial surface. The arrow points from the head. 



Zygapophyses, anterior, much extended, laterally compressed (z); 

 internally nearly plane, slightly oblique; posterior, appear to be 

 only elongated hollows on the neurapophysis (/). 



Beyond the middle of the tail, where all trace of transverse spine 

 is lost, the lengths of the vertebrae are little or not at all reduced, 

 becoming hour-glass shaped. The neural canal is covered for nearly 

 half the length of the vertebra anteriorly ; from this passes back- 

 ward a long ascending process, which bears the posterior zygomatic 

 articulating faces. See Diagram XCI. 



The dimensions of this instructive vertebra are as under : Length, 

 4*25 inches; breadth, 375; height, 3*3; depth of concavity of 

 faces, 0-35. 



Of chevron bones we have five specimens, from the anterior and 

 middle portions of the tail. In Diagram LXXXIX. one is re- 

 presented close to its place of attachment, on the posterior aspect ; 

 the two branches almost in contact. The length of this chevron 

 is 14 inches on the median line, and the breadth over the branches 

 4-75. The whole vertebra, including the neural spine, would be 

 33 inches in height. 



