XIII. 



PLEIOSAURUS GAMMA. 



359 



The dorsal vertebrae which correspond to these are of different 

 proportions : the length being 2*30 inches ; breadth, 3-35 ; height 

 to the canal, 3-32 ; to the border of the canal, 3*40. These pro- 

 portions (100, 145, 144) agree well enough with those of P. 

 brachydeirus. 



Viewed from above, the neural canal is remarkably contracted 

 in the middle ; seen endways, the bases of the neurapophyses slope 



Diagram CLIII. Dorsal vertebra of Pleiosaurus gamma. Scale one-fifth of nature. 

 i. Seen from above. ?. Seen sideways. 3. Seen in front. 



away from the middle more than in our specimens of P. brachy- 

 deirus, but this may vary along the column. 



The articulating surfaces are gently concave round the centre, 

 which is deeply pitted and somewhat wrinkled, two slight hollows 

 diverging upward. 



Of lumbar and caudal vertebrae corresponding to this species 

 we have a series of ten. The largest and most forward in the 



Diagram CLIV. Lumbar vertebra of Pleiosaurus gamma. Scale one-fifth of nature. 

 I. Seen from above. 2. Seen sideways. 



column, having no marks of hsemapophyses, are nearly flat on both 

 faces, which are deeply pitted in the middle. 



