108 PROCEEDINGS OF THE NATIONAL MUSEUM vol.73 



that of the triceps, and 14 of the insertions of Zalofhua and 11 of 

 Phoca have shifted distad. Further scrutiny shows that almost all 

 of these insertions that have shifted distad are muscles of the upper 

 arm and thigh, while of the antibrachial and shank muscles whose 

 origins have shifted half have moved proximad and half distad, 

 an exception being the triceps longus. On the average, therefore, 

 the tendency has been toward a lengthening of the limb muscles, 

 not actually but in respect to the positions of their bony attachments. 



DISCUSSION 



In the following pages Zalophus and Phoca will be discussed as 

 two mammals that are chiefly aquatic, differing from each other in 

 certain respects and from the normal terrestrial carnivore in others. 

 There will be no discussion in the present paper of the probable 

 derivation and but little regarding the relationship of the Otariidae 

 and Phocidae, nor of certain broad principles and laws intimately 

 correlated with the development of a mammal for an aquatic life. 

 It may be mentioned, however, that the writer considers the serious 

 comparison of the otariids with the bears and of the phocids with 

 the otter (as Mivart, 1885), in an attempt to prove that the ancestry 

 of these two pinniped families can be traced to members of groups 

 now living, to be a rather unprofitable pastime. There are many 

 resemblances, it is true, but it is very probable that the eared seal 

 phylum is older than the bears. Not only is the Pinnipedia a very 

 ancient order but the carnivore stem has had very numerous branches, 

 and it is extremely unlikely that the protopinniped.was at all like 

 any living fissiped. 



In all the pinnipeds the relaxed position of the anterior nares is 

 almost closed and naturally remains so between respirations even 

 when the animal is on land, although I have seen a sea lion maintain 

 its nostrils in a dilated position for several minutes at a time, and also 

 a phocid when panting after considerable exertion. Tight closure 

 can be effected both by contraction of the naso-labialis, pulling the 

 mystacial pad against the nostril, and by contraction of the fibers of 

 the mystacial pad itself, which radiate toward the surface and prob- 

 ably have some voluntary muscle action. Expansion of the nasal 

 opening is effected by flexion of the maxillo-naso-labialis, which pulls 

 the mysticial pad laterad. This pad is much broader and thicker in 

 the phocid, but there was apparently no difference in the operating 

 mechanism of the anterior nares to account for it. Possibly the 

 reason for the difference in size of the pads may be found in some 

 variation of the tactile function of the vibrissae. In breathing on 

 land the otariid keeps the nostrils virtually closed between breaths, 

 opens them moderately at exhalation and widely during inhalation. 



