490 University of California Publications in Geology [Vol. 11 



Comparative Measurements of Inferior Dentition of Merychippus Forms* 



OS 'dMr! T3 C. OCi-r o 00 e — CI 



cm go! S grii sa; ani. poo 



V "5,03 c3 T.c rt £010 e« CO 



«ciS " ci a; »'H«i *- « Ji * <m _ 2 in 



° 6 g °6g °6S -og — o g " d 



Length, anterior side P ; to 



posterior side M 3 120.5 123 



Length, anterior side P ; to 



posterior side P 4 60.5 64 75 62 



Length, anterior side M t to 



posterior side M 3 45.2 mm. 60 61 57.6 



P 2 , anteroposterior diameter 21.8 20.5 25.1 21.2 ol8.5 



P,, transverse diameter 10.6 9 10.8 



P 3 , anteroposterior diameter.... 22.2 20.4 22.5 25.1 20.4 18.9 



P 3 , transverse diameter 11.2 12 10.4 12.2 14.2 



P 4 , anteroposterior diameter .... 23.5 20 21.8 24.7 20.4 19.8 



P 4 , transverse diameter 11.6 12.2 10.5 12 14.3 



M„ anteroposterior diameter.. 20.4 18.8 21.6 25.4 18.2 17.5 



M„ transverse diameter 10.6 10.8 9.5 10.1 12.8 



M 2 , anteroposterior diameter.. 20.9 21.1 25.6 18.5 18.2 



M„ transverse diameter 9.4 10 9.7 11.5 9.5 



M„ anteroposterior diameter.. 23.3 21.1 25 22.1 



M„ transverse diameter 7.8 8 9.3 8.8 



Length of crown, P, 38 44 



Length of crown, M 2 a41 



No. 21569 No. 21776 



I„ anteroposterior diameter .... 8 7.7 



I,, transverse diameter 10.3 



I;, anteroposterior diameter .... 8 7.7 



1 2 , transverse diameter 10.7 11.6 



1 3 , anteroposterior diameter .... o6 a5.7 



I„ transverse diameter al0.4 5.9 



C, anteroposterior diameter .... 7 3.9 



C, transverse diameter 6.8 4.3 



* All measurements without cement. For system of measurements see Univ. 

 Calif. Publ., Bull. Dept. Geol., vol. 7, p. 409, 1913. 

 a, approximate. 



Milk Dentition. — The milk teeth of Merychippus forms are well 

 shown in a number of specimens from the Barstow beds, but it is 

 not possible to make certain in every case which of the several species 

 is represented. 



In specimen 19816 (fig. 45, p. 483) a complete upper cheek-tooth 

 dentition is shown with the permanent premolars partly formed in the 

 jaw above. The well worn milk teeth have a pattern suggesting Mery- 

 chippus calamarius stylodontus. They are well cemented and the 



