I 914 ] Taylor: Aquatic Adaptation in the Carnivora 



479 



quadrupeds be likened to fresh-chipped, sharp and angular bits 

 of rock, those of the Enhydrinae are comparable to water-worn 

 pebbles." 27 Evidently the cheek-teeth have entirely lost their 

 sectorial and prehensile functions. 



The tooth formula of Latax j>|> £x2 = 32 ) is somewhat 

 reduced as compared with that of Lutra X2 = 36^ 



The loss of a pair of lower incisors is a modification analogous to 

 the case in seals, which, as is well known, have only two pairs of 

 these teeth. This is one of the points which seemingly indicates 

 that, from an evolutionary standpoint, the sea-otter is traveling 

 in the general direction of the pinnipedian carnivores. 



Carnassials. — One specimen (no. 6956) retains the milk car- 

 nassial in the lower jaw. This tooth was evidently about to 

 be shed. Immediately behind it is the permanent carnassial. 

 The tuberculation of the milk carnassial resembles that in 

 the lower carnassial of Lutra canadensis, which has well- 

 developed protoconid, paraconid and metaconid, with a heel made 

 up of hypoconid and entoconid. These facts probably indicate 

 that the ancestral form from which Latax. is descended possessed 

 a carnassial in form resembling that of Lutra canadensis. An- 

 other item confirming this view is that the milk carnassial is not 

 so flattened and rounded in appearance as the true lower car- 

 nassial, but the ridges and tubercles are more acute. Of course 

 if the food of the young sea-otter after the animal is weaned is 

 different from that of the adult there might be adequate reason 

 for the differences in the form of the carnassial here noted, which 

 differences would then have no phylogenetic significance. There 

 is no evidence, however, that there is any difference in food 

 between adult and weaned juvenal. 



The permanent carnassial exhibits a very great reduction of 

 the paraconid. Reduction and ultimate loss of the paraconid are 

 generally correlated with the assumption of a crushing function. 

 In the case of the sea-otter, the acquisition of a more purely 

 crushing function seems to be associated with aquatic adapta- 

 tion. 



-~ Coues, E., op. cit., p. 325. 



