1881.] PROF. W. H. FLOWER ON THE ELEPHANT SEAL. 155 



be of the same number as the permanent set, and the milk-molars 

 of all Seals, and indeed of the Carnivora generally, are |, corresponding 

 to the second, third, and fourth premolars of the second dentition. 

 There was, in addition, in the upper jaw a small cap of dentine, in the 

 situation of the apex of the first permanent premolar — a tooth which, 

 in its development, is almost coeval with the milk-teeth, and has no 

 predecessor. The permanent dental formula of the Elephant Seal 

 is thus determined to be i. f, c. {, p. j^, m. j- = 30, as given above. 



The incisors and canines are cylindrical, with rounded, rather 

 truncated crowns, and are open at the base. The upper canine, which 

 is the largest tooth, and of which the whole of the crown and greater 

 part of the root are calcified, measure 3 millims. in length and 

 I millim. in greatest thickness. The second upper incisor is about 

 half this size, and the first still smaller. The molars consist only 

 of a rounded crown, scarcely more than 1 millim. in diameter, wjth 

 the commencement of a single root, which, however, is not calcified. 



As the crowns of teeth, once calcified, never enlarge in diameter, 

 we may presume that these rudimentary teeth had attained their full 

 dimensions, except, perhaps, as to the length of the root in some of 

 them. They therefore, in contrast to the size of the animal and of 

 the permanent teeth, represent one of the most rudimentary con- 

 ditions in which it is possible to imagine the existence of a set of 

 milk-teeth complete as to number ; and they form the last term 

 known at present of a series, beginning with the ordinary terrestrial 

 Carnivora, such as the Canidae, and passing through the Bears, the 

 Otariidae, and the other known members of the Piiocidse. The step 

 from this condition to the completely monophyodont state of the 

 Cetacea is not very great. These teeth probably disappear long be- 

 fore birth ; but foetal Elephant Seals at later stages of development 

 are greatly required, in order to trace the progress of dentition. 



Auditory Ossicles. — The auditory ossicles of the Elephant Seal 

 have been described and figured in the elaborate memoir by Mr. 

 Alban Doran on these structures ', which merit more attention than 

 fhey have hitherto received as guides to affinity. Before the pid)- 

 lication of this memoir, or the formation of sucii a collection as that 

 now to be seen in the Museum of the College of Surgeons, it was 

 impossil)le to appreciate their value, as it is only by studying the 

 modifications ot any part in a tolerably extensive series of forms tliat 

 its essential characters can be deduced and separated from tiiose that 

 are variable and comparatively unimportant, and the true relative 

 value assigned to the different modifications met with. 



The auditory ossicles of the Seals generally differ from those of 

 their allies, the terrestrial Carnivora, in their large size and the 

 massive and exuberant growth of the bone composing them. It is very 

 remarkable, and may perhaps indicate some, tiiongh not yet under- 

 stood, relation to the conditions under which these animals live, that 

 in this respect they resemble the other aquatic mammalia, tlie Cetacea 

 and the Sirenia. 



But it is only in this, perhaps an adaptive character, that the 

 ' Trans Linn. Soc. 2ud series, Zoology, vol. i. 



