Remains in Magnesian Conglomerate. 351 



the tooth, — the outline of each tooth thus somewhat resembling a surgeon's 

 abscess lancet, with an elevation extending on the outer side^ down the mid- 

 dle, from the point to the crown. These characters, to be well seen, require 

 a magnifying glass. The middle teeth are the largest, measurin"- not less 

 than a quarter of an inch above the socket : they all possess a conical hollow, 

 filled up by spar, of the same red colour as that already mentioned. No germs 

 of new teeth have yet been discovered ; but this is probably owing to the 

 outer surface only of the jaw being exposed. 



Since writing the above, we have been favoured with a sight of a small por- 

 tion of a jaw (Fig. 3.), in which the alveolary septa and a young tooth are 

 well exhibited : this specimen is in the possession of the Rev. David Williams, 

 of Bleadon. 



From the foregoing characters it is clear, that the remains in question are those of a Saurian. 

 In determining the zoological position of the animal, it is evident, First, That the distinct alveoli 

 of the jaw separate it from the great genus Lacerta of Linnaeus, as reformed by the Baron Cuvier, 

 by rejecting the Crocodiles and the Salamanders, 



Secondly, That the presence of distinct alveoli, is a character by which the animal approaches in 

 structure to the Crocodiles ; but from the lancet form and crenations upon the teeth, althouo-h there 

 is one exception to the latter character, we may conclude that it did not belong to the Crocodiles, 



Thirdly, It cannot appertain to those Lizards whose alveolar inner edge is either wanting or 

 much less elevated than the outer one ; since, in the specimen, the inner edge is of equal height 

 with the outer. 



Fourthly, The same characters, viz. an elevated inner alveolary edge, and distinct alveoli, and 

 the formation of the new tooth in the same cell with the old one, into whose hollow it penetrates, 

 most clearly distinguish it from the Monitors. 



Fifthly, That the number of the teeth, twenty-one, is much greater than in the Monitors, which 

 rarely have more than twelve on a side, and irregular in size and form, while in the fossil animal, 

 they are comparatively regular in both of these points. 



Sixthly, Although some Monitors have flattened and sharp teeth, with their edges finely serrated, 

 a character possessed by our fossil, yet as in the recent animal the cavities, when their growth is 

 terminated, are filled up and become solid, but in the teeth of the extinct Saurian remain perma- 

 nently hollow, another point of difference is established ; thus we consider these characters suffi- 

 cient to exclude the animal from the genus Monitor. 



Seventhly, In the number of the teeth, this jaw much resembles the Iguanas and Scinks ; but 

 the distinct alveoli, and the inner alveolar ridge, and the different forms of the summits and serra- 

 tures in the species here described, are at once sufficient to distinguish it from them. 



Eighthly, In form, position, interior cavity, and developement, they have a nearer resemblance 

 to those of Saurodon of Hay *; but the Saurodon Leanus has the edge of the teeth smooth, 



* Description of a fragment of the head of a new fossil animal discovered in a marl pit, near 

 Morristown, New Jersey, by Isaac Hay, M.D. Transactions of the American Philosophical So- 

 ciety, New Series, vol. iii, p. 471., Plate XVI., 1830. See also the Sketches A. B., Plate 

 XXIX., accompanying this memoir. 



