126 



ME. A. S. WOODWAED 0]S T THE DENTITION 



median area usually occupied by transverse ridges and furrows. 

 Each, tooth is narrowed in front, the blunt anterior end fitting into 

 the slightly forked and broadened posterior end of its predecessor, 

 and the root is extraordinarily deep. 



In the series (tig. 4, 1) immediately adjoining this median row on 

 either side are arranged the largest teeth of the jaw, measuring as 

 much, as 0*025 in a transverse direction, by 0*019 antero-posteriorly. 

 These (fig. 6) are quite of the normal type, rectangular, not much 

 elevated, and approximately equal in size, so far as is indicated by 

 the ten examples preserved. 



The second lateral row (fig. 4, 2) is represented on the left by 

 seven of its components, and on the right by four. These teeth 

 only attain the average dimensions of 0*016 transversely, by 0*013 

 longitudinally, and there is little trace of obliquity ; but a third and 

 much smaller series, of which four teeth remain on the left (3), begin 

 to exhibit a slightly rhomboidal form, and in their fossilized state 

 are directed somewhat backwards. The latter have an average 

 measurement of 0*012 by 0*01, and, like all the others of this jaw, 

 do not exhibit any distinct traces of wearing. 



The main mass does not afford evidence of further lateral rows, 

 though some are evidently broken away from each side. But a 

 detached fragment of the fossil (fig. 7) shows three examples of the 

 right row no. 3, flanked outside with three members of a fourth 

 series, which are again smaller and measure only 0*01 by 0*007. 

 These teeth are very oblique, and seem to have been followed by at 

 least one, and probably more outer rows, though no certain proof 

 is forthcoming. 



Of the opposing jaw, as already stated, only seven teeth are pre- 

 served in their original positions, five of these representing the 

 median series, and the remaining two belonging to the first lateral 

 row on the left. A detached median tooth (fig. 8) also seems to fit 

 in a hollow in the main mass, and this, being divested of all adherent 

 pyrites, may be described as a very typical example. It is rather 

 larger than the largest in the other jaw (fig. 6), and more trans- 

 versely elongated ; and the crown of the tooth has a remarkably 

 conical form, in consequence of the depth of the groove into which 

 it is adapted to fit when biting. It measures 0*032 transversely, 

 by 0*02 longitudinally, and the other corresponding teeth with worn 

 summits are of approximately the same dimensions ; but two asso- 

 ciated examples, evidently just developed and never functional, are 

 of somewhat greater size, having a breadth of 0*036 and a length 

 of 0*023. 



The grinding- surfaces of the two lateral teeth in situ are obscured 

 by contact with the cementing pyritous matrix ; but there are several 

 loose specimens, and one is shown from two points of view in fig. 9. 

 The dimensions are considerably reduced, averaging only 0*026 by 

 0*015 : but there is the same transverse elongation, and the crown 

 is likewise much elevated. It is also noteworthy that the examples 

 showing most evident traces of wearing have a transverse measure- 

 ment as much as four millimetres less than that of the newly 



