14:4 MAEINE EEPTILES OP THE OXEOED CLAY. 



postaxial ; the upper and lower surfaces in this region are much roughened, the bone 

 presenting a peculiar fibrous appearance, seen also in other Plesiosaurs, and being 

 petforated by a number of small foramina running obliquely into the substance of the 

 bone towards the shaft. 



The distal end bears facets for the radius and ulna : the former of these surfaces is 

 the larger and is nearly flat ; it makes a very obtuse arigle with the ulnar facet, which 

 is a little concave. Postaxially the cartilage-covered surface turns upwards on to the 

 posterior border of the distal expansion, and there may have been a small postaxial 

 accessory ossicle as in some other forms. 



The shape of the radius and ulna will be best understood from the figure (PL VII. 

 fig. 2 J) ; it will be seen that they unite with one another by a large proximal surface 

 and a smaller distal one, enclosing between them an almost circular opening. The 

 radius (r.) is considerably larger than the ulna {u.), particularly as to the length of its 

 preaxial border. The postaxial border of the ulna bears three facets, w^hich were 

 cartilage-covered in life and may have supported the pisiform and the postaxial 

 accessory ossicle above referred to. Professor Seeley, in describing these specimens, 

 drew attention to the tendency to the elongation of the radius and the transverse 

 extension of the ulna: this character is better marked in another specimen (R. 3698). 



Distally the radius and ulna articulate wdth the radiale, intermedium, and ulnare ; 

 the radial and ulnar facets for the intermedium are of about the same size. 



In the second specimen (R. 3098) a \eit femur is preserved. In this bone the head 

 is well ossified and convex, its surface being similar to that seen in the humerus 

 described above. The trochanter is large, forming a considerable prominence on the 

 dorsal surface of the upper end of the bone, the ventral surface of which is much 

 roughened for the attachment of muscle ; there is also a short but prominent ridge on 

 the postero-superior surface of the shaft. The distal extremity is less expanded than 

 in the humerus, and the expansion is more equally preaxial and postaxial. 



The surfaces for articulation with the tibia and fibula are nearly flat, that for the tibia 

 being a little the larger. Postaxially the fibular surface passes up for a short distance 

 on to the posterior border of the expansion. The bone here regarded as the tibia is 

 rather longer than broad ; it unites posteriorly at its proximal end with the fibula by a 

 large facet, but does not seem to have touched it distally. The fibula is broader than 

 long and closely resembles the ulna in form. 



E. 1935 (Leeds Coll. 14). A portion of a skeleton including six cer-vical vertebrje, two dorsals, 

 ten ribs, scapula?, coracoids, interclavicle, humeri, one radius, ulnse. Type specimen 

 described and figured by Seeley, loc. cit. supra, as MurcBnosauTus heloclis. (PL YII. 

 figs. 2-4 ; text-fig. 70.) 



The dimensions (in centimetres) o£ this specimen are : — 



