MONOGRAPH 



ON 



THE FOSSIL EEPTILIA 



OF THE 



KIMMERIDGE CLAY. 



Pliosaurus grandis. 



Plesiosaurus grandis, Owen. 'Report on British Fossil Reptiles,' 8vo, 1839, p. 83. 

 Pliosaurus — Owen. Ibid., 1840, p. 54. 



The publication by the Palaeontographical Society 1 of the evidence of the 

 bulk of the Pliosaurus, afforded by a tooth of the Pliosaurus grandis in the 

 Palaeontological Collection of the Hon. Robert Marsham, attracted the attention 

 of other geologists and collectors of fossils to the subject, and stimulated the 

 possessor of a rich series of Pliosaurian remains from the Kimmeridge Clay at 

 Kimmeridge, J. C. Mansel, Esq., of Whatcombe, Dorsetshire, to transmit to me 

 the magnificent tooth which forms the subject of Plate XII. 



This tooth exemplifies its most perfect state of formation ; the entire fang, 

 or root, has been developed, and the unworn state of the crown shows that the 

 time had not arrived for the absorption of the root through pressure of a 

 successional tooth, which undermining process is usually concomitant with the 

 loss of efficiency of the dental instrument through the wearing down of 

 the crown. 



This tooth accordingly presents a total length of 1 foot, one third of which 

 is formed by the enamelled crown, the other two thirds by the cement-covered 

 root. This part expands for the first half of its extent to a diameter of 3 

 inches, which is the thickest part of the tooth, and then gradually contracts to 



1 Volume of tbc Palseontographical Society, 18G1, p. 15. 



