50 MR. R. LYDEKKER ON DINOSATTRS OF THE WEALDEN 



Quite recently Mr. A. N. Leeds of E3'ebur3% near Peterborough,, has 

 added to his unrivalled collection of Saurian remains from the Oxford 

 Clay of that neighbourhood a considerable proportion of the skeleton 

 of a large Pliosaur, which is important as being not only the first 

 example (exclusive of Feloneustes) of the association of teeth, vertebrae, 

 and limbs, but also as being a generalized form connecting the 

 typical Kimeridgian species of Pliosaurus with the smaller forms 

 described as Feloneustes. Mr. Leeds has been good enough to permit 

 me to select such portions of the skeleton as appeared best to illus- 

 trate the alfinities of this form, the description of which I now give. 

 The specimens collected by Mr. Leeds include the greater part of the 

 mandible, showing the entire symphysis, a number of detached teeth 

 in very beautiful preservation, several cervical vertebrae, in some 

 instances with the neural arches and ribs, the greater portion of the 

 pectoral limb of one side, and portions of that of the other, and 

 several bones of the pelvic limbs. 



These specimens indicate an individual agreeing approximately 

 in size with an imperfect skeleton of Pliosaurus hrachi/dirus in the 

 British Museum, ISTo. 46796 *, the cervical vertebrae of both examples 

 being of nearly the same size, and the mandibular symphysis having 

 a transverse diameter of about six inches. The humerus measures 

 nearly 24 inches in length, or slightly more than in the type skeleton 

 of P. brachi/cUrus from Market-E.asen. 



The mandibular symphysis agrees with that of the typical Kim- 

 eridgian species of Pliosaurus in that it extends back as far as the 

 seventh tooth. Except for its much larger size the mandible presents 

 no characters by which it can be distinguished from a probably 

 immature mandible from the Oxford Clay in the Eyebury collection 

 which I have referred f to Pliosaurus ferox. 



Of the detached teeth one of the largest is represented in PI. V. 

 fig. 1, this and other similar ones being the finest specimens of 

 Pliosaur teeth that I have ever seen. Whether this tooth belonged 

 to the upper or lower jaw, there are no means of definitely deter- 

 mining, but it is evidently either from the premaxillary or the 

 symphysial region. The pulp-cavity is open and extends the whole 

 length of the root and some distance into the crown. The crown 

 of this tooth is almost undistinguishable from that of the smaller type 

 of teeth belonging to PeloneusUs philarclius. It also closely resem- 

 bles the Pliosaurian teeth commonly occurring in the Oxford Clay of 

 Peterborough, which are undistinguishable from the Continental 

 examples described under the name of Liopleurodon fero.v, a name 

 which I have altered to Pliosaurus feroxX- It is true that in the 

 present examples the inter carinal space of the teeth of typical 

 Pliosaurs is scarcely definable, and the ridges are rather more con- 

 tinuous and closer together than in typical examples of P. ferox ; 

 yet, after careful comparison with a number of specimens, T find 

 such a transition from the typical form to the present type that it 



* Cat. Foss. Kept, and Amphib. Brit. Mus. pt. ii. p. 124 (1889). 

 t ' Catalogue,' op. cit. p. 145. | ' Catalogue,' p. 145. 



