52 Messrs. Embleton and Atthev on the 



the teeth, being firmly anchylosed to their sockets, could not 

 come out ; but the parts above the alveoli, being firmly im- 

 bedded and entangled in the matrix, have been broken away 

 with it and lost ; moreover the weakest part of the teeth is 

 immediately above the alveolar border. In the case of the 

 right half-mandible, which was obtained with the shale 

 around it, this matrix has been carefully worked and cau- 

 tiously chipped away, leaving the teeth in situ, exposed on 

 their outer surface, but left supported by the shale on the 

 other side. 



There are upwards of twenty teeth in this half-jaw : seven- 

 teen or eighteen are well preserved ; a dozen are entire. They 

 vary much in size, and are irregularly arranged, in some parts 

 being nearly in contact with each other, in others considerably 

 apart. Three are much larger than the rest, and seem to cor- 

 respond to the vomerine and palatal tusks of the upper jaw. 

 These large teeth are 1^ inch long, and upwards of ^ inch 

 across at their bases. The first is placed an inch from the 

 anterior end, upon the eminence already noticed as existing 

 on the alveolar border ; a single small tooth exists in front of 

 this. The second large tooth is 2 inches further back, and the 

 third 1| inch behind the second ; the third is therefore 3f inches 

 behind the first ; but the apices of these two are 4£ inches 

 apart — a distance very nearly corresponding to that between 

 the depressions behind the vomerine and last palatal teeth of 

 the maxilla. No interdental depressions are visible on this 

 exterior surface. The smaller teeth vary from | to about 

 | inch in length. 



The left half-mandible, Plate VI. fig. 3 (represented half 

 the natural size of the fragment), has been crushed, and the 

 posterior part broken off and lost. The greater part, however, 

 9 inches in length (the anterior end), remains in a good 

 state (see vol. iv. ' Nat. Hist. Trans, of Northumberland and 

 Durham,' 1872, p. 392). 



This fragment shows both inner and outer surfaces, and 

 contains twelve teeth, of which three only are large; several 

 gaps exist in the row, the teeth being irregularly placed. 



The teeth as seen from the outer surface are, with one ex- 

 ception, broken off on a level with the outer alveolar border ; 

 but if we look at the inner surface, the alveolar border there is 

 found to lie at a much lower level than the outer, forming a 

 concave irregular line 7 inches long along the jaw, extending 

 from the front of the third tooth backwards to the fractured 

 end ; it descends gradually towards the middle of the jaw, and 

 then similarly rises, approximating to the level of the outer 

 border. This deficiency of the inner border, which at first 



