THE SOUTHERN SEA LION 291 



infrequently lost, as for example in the males 1089 and 1127 and the female 1129. 

 In two other males, Nos. 1138 and 1135 (Plate X, fig. 6), there is a full dentition on 



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the right side, while the left of each is - - - . The last upper cheek tooth is often set 



at some distance behind the others, and it is always small and lightly rooted ; it appears 

 as if the species were in the process of losing this tooth. 



In the adult male one or both of the lower incisors of each side may be lost, and if 

 the animal lives long enough the socket is obliterated. Skull No. 335^ in the National 

 Collection is very fully developed from the osteological point of view and has no trace 

 at all of sockets for the incisors in the mandible: the rami are fused — an unusual 

 condition. It is likely that these teeth are lost in fighting; damaged teeth are not 

 uncommon in the adult males and one can often hear the fangs of the opponents clash 

 together during their combats. The females lose these incisors also at times; but less 

 frequently than do the males. 



In some animals the teeth are much worn; but this alone must be accepted with 

 caution as evidence of age, since animals from sandy places tend to have their teeth 

 more worn than do those from other places, and this difference is observable among 

 the male skulls of my collection (Colyer, 193 1). 



Of the young 



The dentition of the very young pup. No. 1087, may be briefly described. Upper jaw: 

 the four central permanent incisors have erupted and the tips of the fifth and sixth 

 cheek teeth on each side are visible. Lower jaw: the central incisors and the first cheek 

 teeth are visible, but the second incisors barely show. Of the milk teeth the upper 

 and lower canines and the upper second cheek tooth, while in the lower jaw the 

 canine and first cheek tooth and perhaps a trace of the second are visible on the right : 

 on the left side the canines and the second, third and fourth cheek teeth remain. 

 Most of the unerupted permanent teeth may be seen in the dried gum. The milk 

 cheek teeth are simple little knobs like the heads of very large pins (Plates IX, X, 

 figs. i). 



At the age of six months the canines are the only milk teeth left, if indeed they are 

 still present, and they are replaced by the permanent canines before the animal is 

 eighteen months old. 



The male pup No. 11 19 is remarkable for having a number of supernumerary teeth. 



The incisors and milk canines are normal, but in the upper jaws there are on the left 



side seven and on the right side no less than nine permanent cheek teeth, while each 



side of the lower jaw contains six cheek teeth. This animal has therefore a total of 



III'? 



1 — J = 42 teeth, six in excess of the normal number. 



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