62 Soufheni Cross, 



described — an instance in wliich, of eight known examples, only two 

 resemble each other. 



The first problem then which confronts us is the explanation of 

 such variability. It can be no more meaningless than is, as a rule, 

 the remarkably definite form and condition of Mammalian dentition. 

 The question is — can we possibly find the meaning ? 



To my mind there is one point wliicli stands out most clearly in 

 regard to a case like the present. The animal whose teeth are 

 subject to such variation can have no use for a stable dentition. 

 Just as the highly specialised complications of the crowns of the 

 cheek-teeth of Lobodon must have arisen through some very special 

 need of the animal — some very specialised mamier of feeding for 

 which the particular form of tooth must be an advantage — so it seems 

 clear that Oimnatophoca must be an animal, the capture and ingestion 

 of whose food is not affected by changes in its dentition. I go 

 further even than this, since I believe that, as already explained, the 

 animal is in the course of losing its teeth. The dentition shows a 

 condition of extreme weakness. The teeth are small and feeble, and 

 it is to this very feebleness that I feel inclined to attribute the 

 variability as regards the roots. It seems to me, in fact, as if the 

 strength to form a completely double-rooted tooth is frequently 



absent. I would suggest then that except for p.m. — and y the 



double-rooted tooth must be the normal, the single-rooted a variation. 

 My supposition gains strength from the fact that in all the eight 

 skulls there is no instance of a double-rooted first premolar — a 

 variation which should assuredly, one would think, occur, were 

 variations towards strength and not towards weakness the rule. 

 Taking the remaining cheek-teeth of the left side, of sixty teeth 

 49 or over 80 per cent, are more or less double-toothed, while of the 

 remainder many are small, imperfectly formed, or mere " daughter " 

 teeth of one of the supposed cases of reduplications. It seems 

 impossible to doubt then that, following the analogy of other Seals, 

 the posterior cheek-teeth of Ommato2Jhoca are normally double- 

 rooted. 



Lastly comes the question of the supposed reduplication of teeth, 

 a point upon which I have, in the earlier part of this article, followed 

 the nomenclature and suggestions of previous writers. Viewed in 

 the light of my previous suggestions, the possibility of reduplication 

 or the reverse loses much of its importance, since it is probable that, 

 where variation is so rife, it may take the form either of increase or 

 of decrease in the number of the teeth. In the former case the new 



