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University of California Publications in Geology [Vol. ll 



heavier. So far as known P x is larger in the Mascall species. The 

 difference between the temporary teeth seems less than between the 

 permanent cheek-teeth of the Mascall and Barstow forms. As shown 

 in figs. 57a and 58 there is a wide difference between the Mascall 

 and Barstow species in the form of the lower jaw. In the Barstow 

 species, the mandible is much higher and heavier than the slender 

 horizontal ramus of the Mascall species. 



Comparative Measurements of Milk Dentition 



Length, anterior side Dm 2 to pos 



Dm 1 , 

 Dm 1 , 

 Dm 2 , 

 Dm 2 , 

 Dm 2 , 

 Dm 3 , 

 Dm 3 , 

 Dm 4 , 

 Dm 4 , 

 Dm 4 , 



transverse diameter 



anteroposterior diameter 30.2 



transverse diameter 



height of crown 



transverse diameter 



anteroposterior diameter 23.9 



transverse diameter 



height of crown 



M', anteroposterior diameter 



Length, anterior side Dm, to pos 



terior side Dm, 



Dm,, anteroposterior diameter 



Dni;,, transverse diameter 



Dm,, anteroposterior diameter 



Dm,, transverse diameter 



Dm,, anteroposterior diameter 24.6 



Dm,, transverse diameter 



Dm., height of crown 







No. 1678 





No. 19816 



No. 21460 



Mascall 





(ii i .0 mm. 



Q9 



vi 71 













7 Q 









3n 9 





97 





la.o 



91 K 



1 1 .0 





22.5 



24.8 



20.5 





21.7 





18.4 





23.9 



25.9 



21.3 





21 



21.4 







8.5 



17 









23.8 



22.2 





No. 20029 



No. 21461 





No. 2139 



72.5 



a78 



66 





2.8 





4.6 





24.5 





22.8 









11.8 







25.1 



21.8 



23.7 



11.8 



12.5 



12.1 





24.6 



27.9 



23 



a26 



12.2 



al2 



11.9 



15 



13 



16.8 



15 



12.5 



24.5 





20 



a26 



a39 





23 



a43 



a, approximate. 



Skull. — Three specimens show the greater part of the cranium 

 and two others represent portions of the anterior region not well 

 preserved in the better skulls. The several specimens taken together 

 exhibit practically all of the essential characters of the skull. These 

 specimens agree quite closely in comparable measurements and seem 

 all to represent the Mcrychippus calaynarius group. No. 20039 (fig. 

 61), the specimen showing the teeth in the best stage of preservation, 

 seems to belong to the M. c. stylodontus type. No. 21385 (fig. 64a) 

 possibly belongs to M. sumani. 



