I 914 ] Taylor: Aquatic Adaptation in the Carnivora 489 



use of the former. Apparently the uses to which the sea-otter 

 puts its forefeet do not require a large hand. If, as the available 

 evidence seems to indicate, the fore limbs are little used in pro- 

 pulsion, a certain reduction in size would be beneficial to the 

 species, and this reduction would be in the nature of an aquatic 

 adaptation. 



Hind Limbs 



The hind limbs present more evident adaptations than any 

 other part of the skeleton. These adaptations may be set down 

 as follows: (1) Proportional abbreviation of the propodial and 

 epipodial portions of the limb; (2) curvature or backward ex- 

 tension of the limb; (3) distal dilation of the limb; and (4) 

 elongation of digits. Under the first head it should be noted that 

 the femur, tibia and fibula are relatively short. The anterior 

 surface of the femur is longer than in Lutra, causing the distal 

 articular surface to face more posteriorly. This implies a greater 

 backward extension of the limb. As an evidence of distal dila- 

 tion, it may be noted that the feet are lengthened and widened 

 to form oars, or paddles. This dilation is brought about largely 

 by the elongation and spreading of the digits. The abbreviation 

 and backward extension of the limb shows a tendency in the 

 development of the hind limb to parallel that of the fore limb, 

 though the disposition toward a distal dilation opposes this 

 tendency. 



There is no Ugamentum teres in the sea-otter, and consequently 

 no pit in the head of the femur for its reception. This is another 

 evidence in the parallelism of the development between the sea- 

 otter and the seal, in which there is likewise no Ugamentum teres 

 or pit in the femur for its attachment. The environmental 

 medium is of such a nature that apparently it does not require 

 so strong a connection between pelvis and femur as does the 

 medium of the atmosphere. Increased freedom of movement 

 may be subserved by this looser connection, and it is probable 

 that this would be an advantage. Flexibility of the vertebral 

 column, as has already been mentioned, is an aquatic adaptation. 



In the hind limb of the seal modifications analogous to those 

 in the sea-otter are apparent. Two opposing tendencies seem to 



