14 Watson, New Genera of Upper Lias sic Plesiosaurs, 



blood vessels. There are two very distinct facets for the 

 rib, these lie about halfway up the side of the centrum. 



The arch is fused on to the centrum, but its line of 

 junction remains perfectly distinct. The arch is high and 

 very robust, the width across its narrowest point between 

 the prae- and post-zygapophyses being only slightly less 

 than the width of the centrum. The neural canal is 

 nearly circular in section ; it is, however, slightly broader 

 than it is high. 



The prae- and post-zygapophyses are connected 

 together to form a platform from which the short and 

 comparatively feeble neural spine rises. The posterior 

 edge of the neural spine is above the corresponding end 

 of the same centrum, and its anterior end comes about 

 half way to the front of the centrum. The prae-zygapo- 

 physes are short, projecting little, if at all, in front of 

 the centrum ; the post-zygapophyses project strongly 

 backwards, and have a large articular facet. These 

 facets are so directed that a horizontal line drawn on 

 one is parallel to the long axis of the animal ; they 

 are inclined to one another at an angle of 105*^ in 

 one of the posterior cervicals. Between each pair of 

 zygapophyses in the middle line is a pit lying above the 

 neural canal, and presumably lodging the attachment of 

 an intervertebral ligament. 



The most marked difference between the anterior and 

 posterior vertebra^ apart from size, is that in the smaller 

 specimens there is a very marked ridge running from the 

 prse-zygapophysis to the posterior point of junction of 

 the arch and centrum. This ridge becomes almost obso- 

 lete in the posterior cervicals. 



Dorsal vertebrcB. The two well-preserved dorsals 

 which are free from matrix belong to the anterior part of 



