26 FRANK E. BEDDARD 



which actually arrives at maturity is in reality of the milk 

 dentition — a view which is held of the cetacean teeth. But 

 to support this view requires some ' manipulation ' of the facts 

 set forth in the ahove pages, and in the memoir of Messrs. 

 Pouchet and Beauregard. It is true that the labial process 

 in the lower jaw teeth at the symphysis extremity of the 

 jaws is very like the tooth rudiments of Beluga, and in fact 

 many mammals, a likeness which is increased by the fact that 

 this outgrowth does not form a continuous lamina as does its 

 supposed homologue in earlier sections (i. e. at the condylar 

 end of the jaw), but decreases in successive sections and seems 

 to disappear. This, however, need only remind us of the 

 residual lamina (as I regard it) in the upper jaw (see Text-figs. 

 9, 10), which is not a continuous lamina but a series of out- 

 growths. 



A stronger argument in favour of the view advanced here is 

 that on the hypothesis now being considered we should have 

 to pay no attention at all to the conspicuous outgrowths of 

 the upper jaw, which are difficult to explain away as of no 

 importance ami without meaning. But even then, it will be 

 noted, we are left with an undoubted difference between the 

 teeth of the two jaws, lower and upper, which is evident in other 

 characteristics of these organs, and which is set forth in the 

 present section of this paper. 



Peculiarities of Teeth of Physeter and com- 

 parison WITH those of other Mammals. 



It is possible to deduce from the foregoing pages such 

 a comparison, which does not, however, shed a great deal of 

 light upon the zoological relationships of the Cetacea, except 

 perhaps in one of the points raised. 



It is clear, at any rate, that Physeter agrees with other 

 mammals in having the usual two dentitions and — as in many 

 cases — a residual lamina containing the promise or possibility 

 of a third dentition, sometimes abnormally developed farther 

 (e. g. in man). Furthermore, I have shown reasons for believing 

 that the permanent dentition, in this cetacean at least, is 



