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University of California Publications in Geology [Vol. 11 



The occipital condyles are large and wide. The occiput is strongly 

 convex immediately above the foramen magnum, but shows a marked 

 depression, apparently with a median ridge for muscular attachment, 

 just below the marked overhang of the inion. 



The posterior palatine opening is wide anteriorly, its anterior end 

 being opposite the anterior region of M 2 in no. 21385, an individual 

 of advanced age of the Merychippus sumani type. In no. 20039, a 

 younger individual probably of the M. c. stylodontus type, the anterior 

 end of the opening is opposite the middle of M 2 . 



The infraorbital foramen is above the posterior region of P 4 in 

 no. 20039. The postpalatine foramina are opposite the middle of 

 M 2 in the same specimen. 



The reconstruction of the skull shown in figure 60 is based in con- 

 siderable part on specimen 21386, presumably a representative of 

 M. c. stylodontus, with restoration according to the characters of the 

 other skulls available. This restoration may be taken as representing 

 the type like Merychippus calamarius in the Barstow fauna. 



The form of the skull in the Barstow specimens is in general similar 

 to that of Merychippus as known to the writer. In most respects it 

 approaches the type seen in Protohippus sejunctus so closely that no 

 generic distinctions are apparent. Such differences as exist are 

 apparently of specific value. 



Measurements of Skull 



No. 20039 No. 21386 No. 21387 No. 21385 



Length, anterior end premaxillary to pos- 

 terior end occipital condyles 336 mm 



Length, anterior end P 2 to anterior end 



premaxillary 82 



Length, anterior side of orbit to anter- 

 ior end of premaxillary al94 



Length, anterior side M 1 to posterior side 



of occipital condyles 199 196 196 



Length, anterior side M 1 to anterior end 



of premaxillary 138 



crushed 



Width, between inner sides of M 1 52.5 a46 44 



Least width between orbits 96 a90 a83 



Least width across nasal ridge above lach- crushed 



rymal fossae o31 25.3 a36 



Greatest width across zygomatic arches .... al42 120 



Greatest width of occipital condyles 52.5 a57 51.8 



Greatest anteroposterior diameter of orbit 49.5 a50 



No. 21389 No. 21228 

 Height of mandible below an- 

 terior end of M 2 47 51 



No. 20029 



Height of mandible anterior 



end of M, 41 



«, approximate. 



