* 



chap, ix.] TEETH : PINNIPEDIA. 235 



sp., S. America, B. M., 85. 11. 23. 1, has small alveolus behind?^ on each 



side. 

 315. Mellivora (= Ratelus): similar case. Vox Heuglix, ibid. 

 31(3. Meles taxus has normally m\. Skull from Quarternary diluvium 



of Westeregeln has small alveolus behind right w^ and left m 7 -. Another 



fossil skull has m§. Nehring, Arch. f. Anthrop. x. p. 20. [1 Small 



alveolus behind left m* in B. M., 211, L] 



31/. Lutra: case of absence of ^a; Mustela : ^ may be absent. Hensel, I. c. 



PINNIPEDIA. 



With reference to dental Variation in Otariidae and Phocidse 

 there is a considerable quantity of evidence. Id some of the species 

 the frequency of abnormalities is remarkably great. Among the 

 most interesting examples are two cases of reduction in the number 

 of incisors, both occurring in Phoca barbata. These cases are 

 especially important in connexion with the fact that the Seals are 

 exceptional among Carnivores in having a number of incisors other 

 than §, and that among the different sub-families of Seals there is 

 diversity in this respect. 



Taken together, the cases of Variation in the premolars and 

 molars of Seals illustrate nearly all the principles observed in the 

 numerical Variation of teeth. In both premolars and molars there 

 are examples of the replacement of one tooth by two, and in some 

 of these the resulting teeth stand in series while in others they 

 do not. Besides these there are numerous instances of extra pre- 

 molars and molars belonging to various categories. 



As regards the frequency of extra teeth in Seals it may be 

 mentioned that of Phocidae 139 normals were seen, and 11 cases of 

 supernumerary teeth ; of Otariida? 121 normals and 5 cases of super- 

 numerary teeth. 



From the simplicity of the normal dentition and from the 

 diversity of the variations presented, the evidence as to the teeth 

 of Seals may conveniently be studied by those who are interested 

 in the phenomena of Variation without special knowledge of the 

 subject of mammalian dentition. 



Incisors. 



It will be remembered that of Phocidae the sub-family Phocinae 

 (like Otariidae) has normally if, while the Monachinae have if and 

 the Cystophorinas i \. Of Phocinae of various genera and species 

 105 skulls having if were seen, and in addition the two following. 



318. Phoca barbata. Greenland: skull having i\ on both sides 

 (Fig. 54). This skull is a particularly good one and is neither very 

 old nor very young. The teeth stand regularly together and there 

 is no lacuna between them. There is no reasonable doubt that 

 an incisor is absent from each side of each jaw. The shape of the 



