12 GENERA OF fHE FAMILY. 



was the next author who recognized the Walruses as forming a 

 distinct family, which he termed Rosmarida\ In this step, he was 

 immediately followed by Gray,* and by the present writer t in 

 1870. Lilljeborg,! in 1874, also accorded them family rank, as 

 has been the custom of late with various other writers. Gill, 

 in 1872, raised them to the rank of a " superfamily " (Bosma- 

 roidea), treating them as a group co-ordinate in rank with his 

 " Phocoidea," consisting of the Phocidcc and Otariidce. 



Their final resting-place in the natural system has now prob- 

 ably been at last reached, the majority of modern systematists 

 agreeing in according to them the position and rank of a family 

 of the Pinnipedia. To Illiger seems due the credit of first dis- 

 tinctly recognizing the real affinities of both the Pinnipeds and 

 Sirenians to other mammals, and with him originated the names 

 by which these groups are now commonly recognized, the chief 

 modification of ILliger's arrangement being the reduction of the 

 Pinnipedia from a distinct order to the rank of a suborder of the 

 Ferce. 



GENERA. 



The family Odoba'nidw (Triclicchidcc Gray and Brookes = .Ros- 

 Mdt'ida' Gill) includes, so far as at present known, only the 

 existing genus Odobccmts (= Triclieclms of many authors, not of 

 Artedi nor of Linne) and the two extinct genera TrichecJiodon 

 and Alacthcrium, recently described from fossil remains found 

 in Belgium. Alactlierium.,\\ while evidently referable to the Odo- 

 b(?nid(e, differs quite strikingly from the existing Walruses. 

 The parts known are the left ramus of the lower jaw, the greater 

 portion of the cranium (the facial portion and teeth only want- 

 ing), several cervical vertebrae, a portion of the pelvis, and vari- 

 ous bones of the extremities. The rami of the lower jaw are 

 not anchylosed as in the Walrus, and the dentition is quite dif- 

 ferent from that of Odobwnus, that of the lower jaw being I. 2, 

 C. 1, M. 4. The symphysis occupies nearly half of the length 

 of the jaw. Van Beneden describes the skull as resembling in 

 some characters the skull of the Otaries, and in others those of 

 the Morses. The molar teeth he says could not be easily distin- 

 guished from those of the Morse if they were found isolated. 



* Aim. and Mag. Nat, Hist,, 3d ser., vol. xviii, 1850, p. i>29. 



t Bull. Mus. Comp. Zool., vol. ii, p. 21. 



t Fauna ofer Sveriges ocli Norgos Eyggr., p. 674. 



^ Arrangement of Families of Mammals, 1872, p. 69. 



|| Van Beneden, Aim. Mus. d'Hist. Nat. de Belgique, i, 1877, p. 50. 



