HUMERUS OF PLESIOSAURIAN. 25 



teeth justify the term Pliosaurus, and we must fall back upon the first name used 

 as non-committal. It may be that the want of twist or some other peculiarity 

 of the enamel ridges may indicate as much as a specific difference from the Oxford 

 Clay examples. 



Distribution. — The two specimens from Rushden are in the Northampton 

 Museum, and a small tooth from Kidlington in the collection of Mr. E. A. Walford 

 may also belong here. The numerous fine specimens from the Oxford Clay of 

 Peterborough are on almost exactly the same horizon as the type, but the Corn- 

 brash is somewhat below that horizon. 



Vertebra of Muraenosaurus. Plate I, fig. 3. 



The specimen thus interpreted is from Rushden, and contains in its neural canal 

 some characteristic Cornbrash matrix. It is from the middle portion of the dorsal 

 region. (See Seeley, ' Q. J. Gr. S.,' vol. xxxiii, p. 545.) The centrum has the shape 

 of a short dice-box, but is least concave longitudinally along the base ; diameters 

 45 mm. transversely and 37 mm. vertically. The articular surface is slightly 

 concave in the peripheral portion, but round the perforated centre is a low, 

 irregular swelling : on the lateral surface is seen on each side a vascular entrance. 

 The neural arch is entirely united to the centrum, so that the vertebra is full 

 grown. The canal is large, somewhat triangular in shape. A peculiar feature is 

 seen on the upper surfaces of the anterior zygapophyses, which are hollowed out 

 somewhat deeply in the antero-posterior direction for articulation with the 

 preceding vertebra — apparently limiting the principal motion to a vertical one. 



These features, particularly the articulation, seem to recall so much those 

 described by Professor Seeley in Muraenosaurus (' Q. J. Gr. S.,' vol. xxx, p. 107), and 

 the general build of the whole resembles so much that of Cryptocleidus oxoniensia as 

 exhibited in the complete skeleton in the British Museum, and as drawn by 

 Professor Phillips (' Geol. Oxford,' p. 309), which is regarded by Professor Seeley 

 as representing a sub-genus of Muraenosaurus, that we seem justified in going so far 

 as to say that this specimen belongs to that genus. 



Distribution. — Besides this Rushden specimen, which is in the collection of 

 Mr. J. F. Walker, there are vertebras in the York Museum of which no more can 

 be said than that they are Plesiosaurian. 



Humerus of Plesiosaurian. Plate I, fig. 4. 



In the Leckenby Collection in the Sedgwick Museum there is a specimen of the 

 right humerus of a Plesiosaurian not actually labelled as from the Cornbrash, but 

 showing the peculiar dark tint usual to fossils from that bed in Yorkshire, and 



4 



