I 914 ] 'Taylor: Aquatic Adaptation in the Carnivora -485 



Relation of Vertebral Characters to Aquatic Adaptation. — Re- 

 duction of interlocking processes, shortening and heightening of 

 the centra, enlargement of the intervertebral foramina, and 

 thickening of the epiphyses seem all to be correlated with an 

 increased flexibility of the vertebral column, which is an adapta- 

 tion to life in water. Other aquatic animals, as the pinnipeds 

 and ichthyosaurs, exhibit modifications of the same kind. 



Reduction of vertebral processes for muscle attachment may 

 also be an adaptation to aquatic life, in that an animal living in 

 water depends largely on flotation for support, as elsewhere ex- 

 pressed. This would lead to a weakening of muscles otherwise 

 needed for support and of the processes for their attachment. 



The absence of the chevron in the sea-otter may be related 

 to the shape of its tail, which is flatfish dorsoventrally, and to 

 the reduction in importance of the tail. The tail of the seal 

 presents no haemal elements. The evolution of the tail of the 

 sea-otter apparently is following the same direction as that 

 already taken by the seal. 



The porpoise (Phocaena) shows tail development in another 

 direction. In this genus the tail is short, but there are lateral 

 flukes. There are prominent chevrons on the caudal vertebrae, 

 which doubtless have a supporting function through their serving 

 as places of muscle attachment. 



In the sea-otter the loss of the chevron seems to be related to 

 aquatic adaptation through its correlation with the shape of the 

 tail and its reduction in length. In the porpoise the, retention 

 of the chevron and even its further development is apparently 

 an adaptation to aquatic life, through its correlation with the 

 probable continued increase in importance of the tail as a pro- 

 pelling organ. 



Scapula 



The scapula in Latax lutris nereis (no. 6956) is relatively 

 smaller than in the river otter, and not so long anteroposteriorly. 

 The distal narrowing is more marked. The spine is not so 

 prominent, and the acromion is less expanded. The Stanford 

 University specimen has the acromion and spine more developed 

 than in no. 6956. The spine of the scapula in the seal is reduced, 

 and the acromion is still less developed than in the sea-otter. 



