TEETH OF PHYSETER 23 



the other hand the small anterior outgrowth, characteristic 

 of so many of the teeth of the upper jaw in Physeter, may 

 perhaps have heen missed owing to its non-occurrence in the 

 sections actually figured by Kiikenthal. Or the pyramidal 

 outgrowth may have been missed for similar reasons, as 

 suggested above on general grounds. If this be so, then the 

 teeth of Physeter will come more into line with those of 

 other Cetacea, and be less abnormal than the facts described 

 and illustrated here would imply. But again it is as likely — 

 perhaps more likely — that the figure of Kiikenthal is to be 

 compared rather with the lower jaw teeth of Physeter. 



Finally, the fact is to be emphasized that these more 

 basally situated outgrowths of a more or less pyramidal form 

 are only to be found among the teeth which are in the anterior 

 part of the upper jaw ; and it is only farther back that the 

 long filiform outgrowth is to be seen. There is thus a differentia- 

 tion of the upper jaw teeth into an anterior and a posterior 

 series, which is remarkable. 



Comparison of Teeth of Lower and Upper Jaw. 



Having now dealt with the structure of the teeth of the 

 upper jaw, we are in a position to compare them more accurately 

 with those of the lower jaw. There is, I think, on the whole, 

 reason for believing that there are differences between these 

 two series. It is remarkable, however, that Pouchet and 

 Beauregard figure no differences between teeth of the upper and 

 lower jaw in their memoir. Such differences as I shall point 

 out, or recall from the above references, from the teeth of the 

 lower jaw, may be therefore merely a matter of age. Whether 

 this be the case or not, the younger foetus shows the following 

 apparent differences between the two series of teeth — those of 

 the upper and those of the lower jaw. Apart from size, and short- 

 ness of the dental lamina in the teeth of the lower jaw, the chief 

 — and indeed perhaps the only — difference between the two 

 series lies in the fact that whereas the dental lamina has only 

 one outgrowth in addition to that which forms the persistent 

 tooth in the case of the teeth of the lower jaw, there are at 



