above the Coal Formation, in Berwickshire. 41 



porting bone. Even the osseous part of a quadruped's tooth is 

 denser than the surface of this fossil ; but I find I can match it 

 in softness by my specimens of the Ichthyosaurus from the Lias, 

 in which the surface of the teeth can be grooved with the slight- 

 est pressure of the knife, as in this fossil from the sandstone, and 

 indeed in those recent lacertine and ophidian reptiles, in which 

 the teeth are, like those of fishes, without roots or alveoli. In 

 looking at the glistening surface of the osseous teeth of these 

 saurian reptiles, serpents and fishes, one would little expect that 

 soft texture which we find upon trial ; but their softness is admi- 

 rably proportioned to the feeble attachment of their broad base, 

 and to the necessity for their rapid growth and frequent renewal 

 during life. I have compared this tooth with those of the larger 

 loricated reptiles (crocodiles, gavials, and alligators) ; but besides 

 the want of the root, which the teeth of these reptiles have, and 

 the dense texture of these deeply fixed teeth, the fossil wants 

 the longitudinal grooves with which these teeth are so constant- 

 ly and minutely striated. It would be much more difficult to 

 prove, that this is not the tooth of some of the Lacertida, where 

 the teeth approach so near to those of fishes in their form and 

 texture, and density, and want of roots, than to show that it is 

 not like that of any known quadruped or loricated reptile. Tak- 

 ing the fossil tooth as an entire tooth, which has been preserved 

 to us precisely as it fell from the jaw upon the loose sand, and 

 I see no reason to doubt this ; its tapering, conical and curved 

 form ; its soft and bony texture, its suddenly expanded base, the 

 irregular projections and consequent waved outline of that base; 

 its total want of a root to fix it in the jaw, and its wide rough 

 cavity for the pulp at the base, are common characters of the 

 teeth of a thousand osseous fishes at present inhabiting our seas, 

 and have never yet been found, so far as I know, in the teeth of 

 any recent or extinct quadruped. On a superficial inspection of 

 the fossil tooth, any one might suppose (the form of the teeth of 

 quadrupeds being more familiar to most than that of fishes), that 

 it is simply the detached crown of a quadruped's canine tooth 

 which has become softened by fossil ization, and has acquired a 

 fractured margin around its base, by long pressure during the 

 consolidation of the imbedding sandstone. I have compared the 

 density of this supposed enamel with that of the oldest enamelled 



