618 PROCEEDINGS OF THE GEOLOGICAL socteTy. [June 22, 
two outermost of the three bones articulate with the middle one. 
One of these bones lies preaxially ; the other two are postaxial, the 
hindmost corresponding to the wing of the femur. 
The preaxial bone (f) is pentahedral. It has a long proximal 
border, articulating closely (all the joints here are close-fitting) with 
the preaxial facet of the femur, and a rather shorter distal or tarsal 
border. Its mesial border, articulating with the middle bone, is 
shorter still. Its preaxial border, nearly straight, forms the front 
edge of this part of the paddle; it is smooth, transversely rounded, 
and non-articular. At its distal end a very short convex articular 
surface’is intercalated between it and the long directly distal sur- 
face. The following are its dimensions in inches :—Preaxial bor- 
der 3-7; proximal border 4-8; longer distal border 3-1 (its arti- 
cular surface is concave from its dorsal to its ventral margins) ; 
shortest border, between the last and the preaxial one (having a 
smooth convex surface), 1-5. From the preaxial position of this bone, 
it is manifestly the tibia. 
The first postaxial bone (g) is also a pentahedron ; its long trans- 
verse diameter is 4-6 inches, and its short or axial diameter 3 inches. 
Proximally it joins the first postaxial division of the distal surface 
of the femur. Its distal border is formed by two articular surfaces 
(concave in both diameters), which meet, a little behind the short 
axis of the bone, in a salient angle. The line of union of the mesial 
pee of this bone with the tibia nearly cuts the distal angle of the 
emur. 
To the postaxial border of this bone the second postaxial bone (h) 
(the third and hindmost one in the row) articulates. Its proximal 
border articulates throughout its entire length with the femur*. 
Its postaxial border 1s convex and non-articular, forming here the 
posterior border of the paddle; and its short distal (tarsal) articular 
border makes with that of the middle bone a deep reentering angle. 
The transverse diameter of this bone is 5°7, and its axial diameter 
3:4 inches. j 
The characters of the early cervical vertebrae and the long taper- 
ing neck prove beyond doubt this spinal column to be that of a Ple- 
siosaurus, and differentiate it from the subgenus Pliosawrus as 
hitherto defined. From the length of the column (in its present 
incompleteness 15 feet) Mr. Mansel’s Plescosawrus must have 
attained a size as great as, perhaps greater than, P. megadeirus 
(Seeley), another Kimmeridge Plesiosaurus, represented by two series 
of associated bones from Haddenham and Ely, preserved in the 
Woodwardian Museumt. ‘The absence of any published account of 
these fossils has prevented me from instituting so searching a com- 
parison of them with Mr. Mansel’s Plestosaurus as I could have de- 
* A line running from near the outer end of this border to the posterior 
border separates the proximal and posterior corner from the remainder of the 
bone. J am doubtful whether this is an accidental or a natural division ; if the 
latter, the piece so separated is a fourth enemial element. 
+ Catalogue of Ornithosauria, Aves, and Reptilia from the Secondary Strata, 
in the Woodwardian Museum, by H. G. Seeley, p. 97. : 
