398 



vests upon the edge of inclined strata of mountain limestone, filling 

 up theirregidaritiesof their surface, and consists of angular fragments 

 of the limestone cemented by a dolomitic paste. The thickness of 

 the deposit at the point where the remains were discovered does not 

 exceed twenty feet. 



Of the three animals described in the paper^ two belong to a genus 

 for which the author proposes the name of Palseosaurus, and the third 

 to one which they have called Thecodontosaurus. 



The characters of the genus Palseosaurus are derived from the 

 teeth, which are described as being carinated laterally, and finely ser- 

 rated at right angles to the axis. They are stated to differ from those 

 of all the Saurians known to the authors : and as the teeth in 

 their possession exhibit minor marked characters, they are induced to 

 consider that they belonged to two species, which they have named 

 P. cylmdriciim and P. Platyodon. 



The genus Thecodontosaurus is likewise founded on the struc- 

 ture of the teeth, and their having been deposited in distinct alveoli. 

 Among other remains in the Museum of the Bristol Institution is 

 the right ramus of a lower jaw, 3^ inches long and 1-j- in the greatest 

 depth, from the summits of the teeth to the under rise, consisting 

 of the dental bone, containing 21 teeth, with portions of the sub- 

 angular and complementary bones, and perhaps traces of the oper- 

 cula. The alveolar groove for the reception of the teeth is formed by 

 two ridges of nearly equal height, the teeth being deposited in it, in 

 distinct alveoli, to nearly half their length. The teeth somewhat re- 

 semble in shape a surgeon's abscess-lancet, being acutely pointed and 

 flattened ; while the anterior edge is also curved, but concave and 

 strongly serrated, the serrature being directed towards the apex of 

 the tooth. The middle teeth are the largest, rising not less than a 

 quarter of an inch above the socket. They all possess a conical hol- 

 low, and in a specimen belonging to the Rev. D. Williams a young 

 tooth is well exhibited in one of the alveolar cavities. From these cha- 

 racters the authors infer that the jaw belonged to a Saurian, but not 

 to the great genus Lacerta of Linnaeus as reformed by Cuvier by re- 

 jecting the Crocodiles and Salamanders. They further infer from the 

 shape and serrated edge of the teeth that it did not belong to the 

 Crocodiles ; nor to the Lizards, whose alveolar inner edge is either 

 wanting or much less elevated than the outer. They also show that 

 it was not allied to the Monitors, because of the elevated inner alveolar 

 edge, the distinct alyeoli, the teeth remaining hollow and the 

 formation of the new tooth in the same cell with the old one, as well 

 as from the great number of the teeth. With respect to the Iguanas 

 and Scinks they show that the fossil could not have belonged to them, 

 in consequence of the distinct alveoli, the inner alveolar edge, and the 

 form of the summit and serratures of the teeth : and that it differed 

 from the Saurodon in having a ridge on the outside of the tooth with 

 the edge crenated and of unequal length. 



Numerous other bones have been discovered, but as none of them 

 were found in connexion with teeth, the authors hesitate to assign 

 them to either of the genera which they have established. Among 

 these remains the following are described ; 



