KIMERIDGE CLAY. 
105 
(loc. cit.), the cervicals of P. brachydeirus are given a length of 
1^ inch, breadth 5 inches, depth 6 inches ; and yet the dorsals are 
4 inches 3 lines broad, 4 inches deep, and 3 inches long. 
Besides these there are in the Collection two anterior cervical 
vertebrae which appear to belong to a third species. (Case 84. e .) 
One is 6^ inches deep, inches broad, 2\ inches long. It has 
a double articulation for the rib, which is below the centre of the 
centrum. From one rib facet to the other it measures 7| inches. 
The other centrum is 6 inches deep, 61 inches broad, and 2 J long. 
In all other respects it is like the first one. 
The most important parts of the skull preserved are the quad¬ 
rate bones with the articulations for the lower jaw (over Cases 87 
and 88). The more perfect of these fragments is 19 inches long and 
a foot wide. The quadrate of Plesiosaurs, Steneosaurs, and allied 
forms is a pedicle projecting backward, while in the Nothosaurs 
it is a pedicle projecting downward and united with the bones at 
the back of the skull, so that, by the union of the ex-occipital with 
the quadrate near the condyle, and of the parietal and squamosal 
bones above, a large foramen, which looks backwards, is made on 
each side of the occipital surface. 
In Pliosaurus the quadrate bone is a slender style which unites 
with the bones of the back of the head exactly as in Nothosaurus, 
only with this difference, that the ex-occipitals encroach much more, 
and produce a smaller “quadrate foramen,” judging from the form 
of the condyle and the general analogy to Nothosaur. 
