392 University of California Puhlications in Geology [Vol. 12 



square form, however, it differs from the usual milk tooth. It suggests 

 in some ways Pliohippus fairbanksi, a form otherwise entirely un- 

 represented in the collection. 



Figs. 126o to 126c. PlioMpptis upper milk teeth. Fig. 126a, no. 23202, inner 

 view, X occlusal view, X 1. Fig. 1265, no. 23220, occlusal view, X 1; fig. 

 126c, no. 23330, occlusal view, X 1. Eden beds, California. 



The teeth nos. 23202 and 23330 (figs. 126a, 126c) have some of the 

 characters seen in the advanced Pliohippus, but their very narrow 

 and short crowns indicate that they are milk teeth. 



fl) A group (see description below) in which the specimens 

 exhibit advanced Eqmts character, in the anteroposterior elongation 

 of the metaeonid-metastylid column, and in the flattening of the 

 exterior faces of the protoconid and hypoconid. The section appar- 

 ently embraces teeth of at least two subforms; these may correspond 

 with the upper teeth described under Plioliippus osborni and P. 

 oshorni, subform A. 



(2) To a second group (see figs. 132-157c) has been assigned the 

 balance of the lower teeth, which though separable into several forms 

 are all of general average Pliohippus character, and are believed 

 referrable to forms lying close to the new species Pliohippus edensis 

 and subforms described under Upper Teeth. The subdivisions of this 

 group are: (1) Medium sized lower teeth, near ( 1) Pliohippus edensis, 

 n. sp. ; (2) large lower cheek teeth near(?) subform B of the same; 

 (3) teeth of narrow transverse diameter; (4) lower cheek teeth of 

 remarkably small size and of uncertain relationship, and (5) speci- 

 mens representative of the milk dentition. 



126a 



Lower Cheek Teeth 



