402 University of California Publications in Geology [Vol. 12 



Description. — The specimens represent peculiar and individual 

 phases of specialization. They are all long-crowned and are remark- 

 able for their transverse narrowness and generally small size. 



A small, slighly worn premolar, no. 23292 (fig. 153), is of inter- 

 esting and unusual type. A cross-section at the root shows the 

 retention of the same characters in the more advanced stage of wear. 



A long, narrow-crowned molar (no. 23290) is especially noticeable 

 for its very small size, even in comparison with the following three 

 small teeth. It somewhat suggests the constricted molar (no. 23197, 

 fig. 128) described under the P. oshorni group, but is infinitely smaller. 



Molar no. 23517 (fig. 154) is somewhat larger than the last. 



A third molar (no. 23227, fig. 155) is unique in having its root 

 more strongly recurved and in being narrower transversely than other 

 last molars of the collection. 



Measueements 



No. 23290 No. 23517 



Anteroposterior diameter 22.5 nun. 25 mm. 



Transverse diameter 8.1 11.7 



Anteroposterior length of metaconid- 



metastylid column 10.1 12.2 



No. 23292 No. 23227 



22 mm. 25.5 mm. 



11 10.7 



11.2 9 



Lov^ER Milk Teeth 



Material — Three milk cheek teeth, Univ. Calif. Coll. Vert. Pal. nos. 24054, 

 23513, 23514 (figs. 157a-157c). 



157b 



157a 



157c 



Figs. 157a to 157c. fPliohippus,. sp. Milk teeth, occlusal views, X 1. Fig. 

 157a, no. 23513; fig. 157b, no. 24232; fig. 157c, no. 23514. Eden beds, California. 



Discussion. — The teeth are of very narrow form, are extended 

 anteroposteriorly, and have very short roots, as is usual in the case 

 of the milk dentition. 



