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University of California Publications in Geology [Vol. 9 



This species includes the smallest members of the Merychippus 

 series in the Barstow Miocene. It is closely related to Merychippus 

 calamarius, and may possibly represent merely a variety of that 

 group. In the characters of the cheek-teeth this species approaches 

 Hipparion, from which it is distinguished by the more strongly curved 

 crowns of the upper teeth, and by the greater simplicity of the enamel 

 borders of the cement lakes. The cement covering of the cheek-teeth 

 is commonly thinner than in Hipparion, and there is no evidence of 

 functional cement on the milk molars. 



Named in honor of John R. Suman who furnished the first specimen 

 of this species used in study of the Mohave Tertiary faunas. 



Measurements of Type Specimen, No. 21422 



Length, anterior side M 1 to posterior side M 3 57 mm. 



P 4 , anteroposterior diameter 22. 



P 4 , transverse diameter 20.8 



P 4 . height of crown 31.3 



M 1 , anteroposterior diameter If). 



M 1 , transverse diameter 19.4 



M 1 , height of crown 28.5 



M 2 , anteroposterior diameter 20.8 



M-, transverse diameter 18.1 



M 2 , height of crown 32.8 



M 3 , anteroposterior diameter 19.7 



M 3 , transverse diameter 15.5 



M 3 , height of crown 32.6 



MERYCHIPPUS INTERMONTANUS, n. sp. 



Type specimen, no. 21400. An upper cheek-tooth dentition from locality 

 1401 in the Barstow Miocene of the Mohave Desert, California. 



Cheek-teeth large; crowns long, strongly curved, heavily cemented. Proto- 

 cone of upper cheek-teeth uniting early with protoconule. Enamel walls border- 

 ing the fossettes comparatively simple. 



This form includes the largest members of the Merychippus type 

 in the Barstow Upper Miocene of the Mohave Desert. It is dis- 

 tinguished from the typical Merychippus calamarius by its larger size, 

 longer crowns, heavier cementation, and more pronounced tendency 

 to union of the protocone and protoconule even in young individuals. 

 The species more closely approaches the Protoliippus type than does 

 typical M. calamarius, and might by some authors be included within 

 the limits of that genus. It is here referred to Merychippus rather 

 than to Protoliippus, as the milk dentition of a number of specimens 

 presumably representing this type seems to show less cement on the 

 crowns of the cheek-teeth than in typical Protoliippus 



