R. S. Lull — Fossil Dolphin from California. 213 



coupled with a more robust angle in the fossil implies a greater 



proportionate jaw power in the older form. In the latter the 



symphysis is apparently longer, though the distal two-thirds 



of each jaw is about equal in slenderness. 



40 

 Dentition. — The dental formula of Deljphinus is — . In the 



fossil the number of teeth in the upper jaw is exactly the same, 



Fig. 2. 



Fig. 2. Right lateral aspect of skull and jaws. % nat. size. Bo, basi- 

 occipital; C, condyle of jaw ; D, dentary ; Exo, exoccipital ; Fr, frontal; 

 J, jugal ; Max, maxillary ; Nas, nasal ; Oc, occipital condyle ; Pa, parietal ; 

 Pmx, premaxillary; Pn, ? posterior nares; Sq, squamosal; So, supraoccipital. 



but the imperfection of the mandible renders a count of the 

 lower dentition impossible. There is no reason, however, to 

 suppose that the number here was not also essentially similar. 

 In each instance the premaxillary bone is toothless. 



The teeth themselves are also alike, being simple, slightly re- 

 curved cones without carinse, and with smooth, polished enamel. 

 They contrast sharply with the spatulate crowned teeth of 

 Phocoena. 



In so far as I am able to judge, the skull and dentition of the 

 fossil agree essentially with those of Delphinus, the exceptions 

 being all in the direction of greater cetacean specialization on 

 the part of the latter, such as the character of the occiput, the 

 reduction of the zygomatic arch, and the lessened jaw power. 



