350 Dr. Riley and Mr. S. Stutchbury on Saurian 



and to be in the place of a great part of the Thuringerwald system*. It is 

 therefore hoped, that the discovery of the Saurian bones described in this 

 paper, will materially assist in connecting- the dolomitic breccia of Bristol 

 with the beds which contain the fossil Monitor of Thuringia. 



We now proceed to describe the bones which we have obtained. 



Plate XXIX., fig. 1. natural size ; fig. 2. magnified three times. 



Fig. 1. A portion of the right ramus of a lower jaw fractured into three 

 pieces, and containing twenty-one teeth. 



Its outer surface is completely exposed, but the inner is imbedded in the 

 rock, and cannot be observed. The length of the specimen is 3^^ inches, and 

 at an inch and a half from the anterior extremity, where the teeth are perfect, 

 the depth from the apices to the inferior edge of the jaw is —ths of an inch. 

 The external surface is convex vertically, and slightly curved inwards, antero- 

 posteriorly, both below and above. 



The fragment consists of a dental and portions of the sur-angular or coronoid 

 bones. Of the denial bone, the greater part remains ; but of the other there 

 are imperfect portions only. Posteriorly and internally may be traced a white 

 line separated by the matrix, and parallel with the preceding: it is probably 

 the remains of the opercular bone. 



Seven foramina are arranged in a line for the inferior maxillary nerves and 

 vessels, and are contained in a groove, shallow anteriorly, but increasing in 

 depth posteriorly; at which part the external bone is broken away, so as to 

 expose the sub-maxillary canal filled with spar of a red colour. The upper 

 edge, forming the alveolar groove of the dental bone, contains the teeth al- 

 ready mentioned; and, from its transverse fractures, it is evident, that this 

 groove is formed by two ridges, the inner being as high, or nearly as high, 

 as the outer ridge, so that the teeth are inclosed in the dental bone to nearly 

 one half of their whole length. The spaces between the teeth in the groove, 

 are filled up with spar ; and at the posterior part only can we observe any 

 transverse septa, so as to constitute distinct alveoli. 



There were apparently twenty-one teeth in the ramus ; and from their de- 

 creasing in size towards the backof the jaw, it is more than probable, that that 

 was the complete number. 



The teeth are acutely pointed, fig. 2. and flattened, and the anterior edge 

 is curved backwards, and serrated; the posterior edge is also slightly curved, 

 and strongly serrated, the serratures being directed towards the apex of 



* See Prof. Sedgwick's Memoir on the Magnesian Limestone, Geological Transactions, 2nd 

 Series, vol. iii. p. 122. 



