104 
PLESIOSA URIA FROM THE 
The reason for thinking this a good species is that many 
specimens have been found exactly of the same size, while there 
are no examples of sizes intermediate between this species and the 
next. The larger specimens almost invariably show a central pro¬ 
minence where this is concave, and differ a little in the proportions 
of the centrum. 
Pliosaurus brachydeirus. 
Of thi3 form the Museum contains but one neck vertebra, 
Case 84 .f. 1, which, from the way the facets for the pleurapo- 
physes adjoin those for the neurapophyses, appears to be the last 
cervical. It was obtained from the Kimeridge Clay of Cottenham, 
and presented to the University by the Rev. S. Banks. It has the 
same concave exterior and the same flattened ends, with a large 
elevated central boss an inch in diameter, between which and the 
peripheral margin the surface is concave. It is nearly 5 inches 
wide, nearly 4^ inches high, and nearly 2| inches thick. 
The sub-circular facets for cervical ribs are not on the surface 
of the centrum, as in Pliosaurus brachyspondylus , but on pedicles 
an inch long. From one pleural facet to the other it measures 6^ 
inches. The neural canal is 2 inches wide behind. Another cer¬ 
vical from nearer to the head has all the same characters, except 
that the bone is half an inch deeper. Of this species the collec¬ 
tion contains 11 dorsal vertebrse in Case 84 .f 
The largest has the articular surface circular and measures 4 j 
inches deep, and nearly 5 inches broad, and 3^ inches long. 
The smallest dorsal has the articular surface vertically ovate 
and measures 4^ deep, and from side to side nearly 3 inches long 
at the base, and a little less at the neural canal. As in the other 
species, the bones show an anterior obliquity. 
It is evident from Mr Conybeare’s figures, pi. 22 (loc. cit.), 
that the cervical vertebrse of Pliosaurus, like those of Plesiosaurus, 
elongate as they near the back, and do not, as stated by Prof. 
Owen*, maintain the same length. There is an anomaly in Prof. 
Owen’s measurements, for, though stating that as the cervical ver¬ 
tebrse recede from the head they increase in breadth and depth 
* P 63, Report on British Fossil Reptiles, Part 11., 1841, British Associa¬ 
tion Reports. 
