TKUE : THE TYPE OF ANOPLONASSA FOKCIPATA 103 



from the section to which the recent genera belong. Leaving out of 

 consideration other fossil forms presently to be mentioned, one might 

 properly separate the Ziphiinae from the Physeteridae and, following 

 J. E. Gray, give them the full rank of a family. The family would be 

 divided into three sections, consisting respectively, (1) of Hyperoodon, 

 (2) the other recent genera, and (3) Anoplonassa. 



Very recently Dr. 0. Abel has called attention to three fossil forms 1 

 two of which at least are somewhat closely allied to Anoplonassa. These 

 are Palaeoziphius scaldensis (Du Bus), Cetorhynchus atavus Abel and 

 Mioziphius belgicus Abel, all from the Upper Miocene of Antwerp. Of 

 these, P. scaldensis is considered by Abel to be the oldest. The size 

 of the mandible is about the same as in Anoplonassa. The length of 

 the entire symphysis in proportion to its depth is about the same as the 

 length of the fragment of the symphysis of Anoplonassa to its depth. 

 Palaeoziphius, however, has 14 alveoli on each side, between most 

 of which are well-formed septa whose upper surface is in the same plane 

 with the upper surface of the jaw. Dr. Abel states that the anterior 

 end of the jaw is slightly expanded, but the figure which accompanies 

 his description does not indicate such an expansion, and we may suppose 

 that it is at best only slight. It is also stated that the symphysial 

 region is semicircular in transverse section and that the end of the jaw 

 is turned upward. 



In Cetorhynchus, which is larger than Anoplonassa, the alveolar 

 groove is rudimentary and the septa are imperfect and do not reach the 

 level of the upper surface of the jaw. This upper surface is concave, 

 while on the sides of the mandible there is a deep mental groove. The 

 transverse section of the jaw is semicircular. 



In Mioziphius belgicus the mandible is much more slender than in 

 Cetorhynchus, but, judged by the symphysial region, is about a half 

 larger than Anoplonassa. Instead of a series of well-formed, or imperfect, 

 alveoli, it has a narrow and shallow rudimentary alveolar groove and 

 two pairs of very large alveoli resembling those of Anoplonassa very 

 closely in some particulars, though the second pair is larger in propor- 

 tion to the terminal one than in that genus. The terminal alveoli are 

 filled with a mass of cancellous tissue which has a concave surface and 

 a central eminence, as in Anoplonassa, and the alveoli themselves are 

 separated by a narrow median partition. The jaw is expanded at the 

 end where these alveoli are situated. The mass in the posterior alveoli, 

 beside filling the cavity of the latter, appears to protrude considerably 



1 Mem. Mus. Roy. Hist. Nat. Belg., 1905, 3. 



