BRITISH FOSSIL REPTILES. 81 



observed in the corresponding part of any other Plesiosaur. 

 The distance from the upper margin of the posterior oblique 

 process to the inferior apex of the neurapophysis exceeds the 

 vertical diameter of the body, and is double the extent of that 

 part of the centrum below the neurapophysis. The articular 

 base of the neurapophysis extends inwards above the centrum, 

 so as to form part of the floor of the spinal canal : the inner 

 surface of the neurapophysis is traversed by a longitudinal ridge. 



The spine of the vertebrae here described was unfortunately 

 broken off. 



I have not met with any other example of a Plesiosaurian 

 vertebra agreeing with the one above described, except a few 

 from the Bristol lias above specified. 



Among these is a centrum of the dorsal series of vertebrae, 

 which, from the character of the anterior and posterior articular 

 surfaces, and the rugose lateral and inferior surfaces, belongs, 

 in all probability, to the same species. It is relatively more 

 compressed in its general form : but we may observe the same 

 difference between the cervical and dorsal vertebrae of the PL 

 dolichodeinis. 



Admeasurements of the above-described Cervical Vertebra. 



Inches. Lines. 

 Antero-posterior diameter of the body . . 1 6 

 Transverse diameter of the body .... 2 



Vertical diameter 1 9 



Dorsal Vertebra. 



Antero-posterior diameter of body .... 1 6 



Transverse diameter 2 9 



Vertical diameter 2 6 



Plesiosaurus daedicomus* . 



Of this well-marked species the humerus is preserved in the 

 collection of Sir Philip Egerton : the specific name relates to 

 the peculiar form of that bone, which resembles a flattened 

 spoon in the narrowness of the shank or shaft, and the remark- 

 able expanse of the distal extremity. The breadth of this part 

 equals one half of the entire length of the bone, and is five times 

 greater than the breadth of the proximal extremity. The shaft 

 gradually expands from the proximal end, and exhibits the flat- 

 tened form characteristic of the genus. There is no trace of a 

 tuberosity at the proximal extremity. 



* So/3y|, a spoon ; ufcof, humerus, or arm-bone. 

 voL.viir. 1839. g 



