MIOCENE PORPOISES — KELLOGG 147 



Eighteen are posterior teeth with accessory cusps and tubercules, 

 of which three were in place in the mandible. On most of these teeth 

 the apex of the cro^vll curves inward and backward. Five teeth, 

 presumably from near the middle of the tooth rows, have the enamel 

 on the outer surface of the crown ornamented with fine striae. There 

 are 28 anterior teeth having crowns with nearly smooth enamel, 

 although a number of them have a fine, vertically directed carina on 

 the outer surface. 



The anteriormost teeth (pi. 21, figs. 7, 8) are characterized by an 

 elongated root, high anteroposteriorly compressed and inwardly 

 recurved crown, and several irregular striae on the basal half of the 

 outer face. 



A few of the posterior teeth (pi. 20, figs. 2, 6; pi. 21, fig. 2) possess 

 a thin denticulated and curved carina on the external face of the 

 crown extending to or almost to apex of the main cusp in addition to 

 one or more accessory tubercles on the posterior face as well as a row of 

 fine denticles. Other posterior teeth (pi. 20, fig. 4; pi. 21, fig. 3) 

 are characterized in part by the presence on the posterior face of a 

 fairly large accessory cusp that has a denticulated cutting edge and 

 one or more smaller tubercles. This posterior cusp varies consider- 

 ably in size and shape, but is set off sharply from the main cusp of the 

 crown. At least three of these teeth (pi. 20, fig. 7) have three or more 

 small tubercles, one above the other, on the posterior cutting edge. 

 One tooth has a well defined and distinct cusp above the base of the 

 crown on both the anterior and posterior faces. The ornamentation 

 of the enamel on the inner face of the crown of these posterior teeth 

 (pi. 21, figs. 3-5) is rugose to a varying degree. On most of these 

 teeth the rugosities on the enamel of the inner face terminate about 

 2 mm. above the base of the crown and are arranged in more or less 

 vertical striae, of which there are on some teeth five or six. On 

 others there is a less definite arrangement of these minute denticles. 

 Several teeth have the enamel (pi. 20, fig. 3) on the inner face of the 

 crown ornamented with minute denticles, the sculpturing being rather 

 coarse above the relatively smooth base of the crown. The enamel 

 on the outer face of the crown is either relatively smooth or rather 

 faintly striated. The teeth located near the posterior end of the tooth 

 rows have shorter and wider crowns than the anterior teeth, and the 

 apical portion of the main cusp is curved either backward or inward. 



There is an evident transition to a few intermediate teeth (pi. 21, 

 figs. 1, 6). On these teeth the development of the tubercles is much 

 less obvious, the crown is longer and differently curved as well as 

 compressed or flattened in an anteroposterior direction. The enamel 

 on the crowns of most of these teeth is somewhat smoother than on 

 the posterior teeth and the crowns are longer and rather slender. 



