1913] 



Merriam: Fauna of Orindan and Siestan 



379 



barely possible that other tubercles were present, but in the 

 present worn condition of the crown no evidence of other features 

 appears. This tooth is near the stage of advance in Tayassu, 

 but is perbaps a little less advanced in that the posterior root 

 is narrower and not distinctly divided. If the crown were com- 

 plete it might show the posterior tubercle or cusp divided into 

 two. This tubercle is, however, smaller than in Tayassu. 



The tooth considered to represent P 3 is nearly quadrate, the 

 hypocone region being slightly less developed than the protocone 

 region. The posterior or hypocone-metacone region is narrower 

 anteroposteriorly than the protocone-paracone region. The stage 

 of advance of this tooth is approximately that of Tayassu. 



P 4 is quadrate in outline, but the hypocone-metacone region 

 is narrower than the protocone-paracone region. The stage of 

 advance is near that of Tayassu. with a tendency to show a 

 smaller posterior lobe than in the Siestan form. 



The proportions of M 2 and M 3 are much as in Tayassu or in 

 Prosthennops. 



The material available indicates that the form represented 

 by specimen 19826 is near the stage of development of Tayassu 

 with the exception that the premolars are slightly less advanced. 

 The character of the upper canines and the length of the diastema 

 are not known. 



So far as represented, the characters in this specimen are those 

 of the genus Prosthennops known from the Upper Miocene and 

 Lower Pliocene. A specimen from the Pliocene of Thousand 

 Creek in northern Nevada referred to Prosthennops 1 resembles 

 this specimen in the general proportions of the teeth, but appar- 

 ently differs somewhat in the character of the crowns. As nearly 

 as one can judge from the imperfect material, P- is quite differ- 

 ently constructed in the two forms. Prom the evidence available, 

 it does not seem probable that they represent the same species. 



Although the material is not at hand for a satisfactory com- 

 parison of the Siestan specimen with the Prosthennops species 

 known east of the Rocky Mountains, it is probable that the 

 Siestan form is distinct from any of the described species. 



i Merriam, J. C, Univ. Calif. Publ., Bull. Dept. Geo!., vol. (5, p. 273, L911. 



