170 PROCEEDINGS OP THE PALEONTOLOGICAL SOCIETY 



known at the present time includes a number of forms not previously recog- 

 nized. A complete list of the known vertebrate and invertebrate species is 

 presented with tentative conclusions as to the age of these beds. 



NEW MIOCENE MAMMALIAN FAUNA FROM THE TEHACHAPI REGION 

 BY JOHN P. BUWALDA 



(Abstract) 



The paper is a discussion of a new mammalian fauna of Middle or Lower 

 .Miocene age, obtained from strata in the summit region of the southern 

 Sierras, near Tehachapi. The determinable material in the collections thus 

 far obtained represents a small camel and one or more new forms of horses 

 of the MerycMppus type, which seem to be of a more primitive stage of evolu- 

 tion than any species within the genus MerycMppus heretofore known in 

 America. 



The strata containing the mammalian remains have been cut by the faulting 

 of the southern Sierras ; the age of the fauna sets a lower limit for the date of 

 at least the major part of this displacement. 



Discussion 



Dr. J. C. Merriam emphasized the importance of the discovery of this type 

 of a tooth which so closely fulfills the prediction of Mr. Gidley regarding a 

 form of a horse which would bridge the gap between the anchitherine and the 

 protohippine groups. 



THE BISON OF RANOHO LA BREA 



BY ASA C. CHANDLER 



{Abstract) 



In Bison antiqitus individual variation occurs in size and relative measure- 

 ments of the skull to tbe extent of about 20 per cent, while the sex differences 

 of these characters are small, being apparently less in B. cuitiqinis than in 

 B. bison or B. bonasus. The horn cores show approximately similar individual 

 variations within a sex, but the average length in females is about 25 per cent 

 less, while the basal circumference is about 33 per cent less than in males, 

 there being no individual overlap in either case. The variation in general 

 form, curvature, and angle of insertion of the horn cores is slight, and these 

 are, therefore, reliable specific characters. The teeth of B. antiquus generally 

 have the enamel walls of the lakes more complicated than those of B. bison. 



STRUCTURE OF THE POSTERIOR FOOT IN THE MYLODONT SLOTHS OF 

 RANCHO LA BREA 



BY CHESTER STOCK 



