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University of California Publications in Geology [Vol. ll 



type specimen. This form is described below as M. calamarius stylo- 

 dontus. It is characterized (figs. 43 to 45) by relatively large size, 

 approaching that of M. intermontanus, simple protocone nearly cir- 

 cular in cross-section and often separate from the protoconule until 

 the crown is worn down to a height measuring much less than the 

 width of the crown, and relatively simple enamel folds. The crowns 

 are wide and well cemented. 



Fig. 40. Merychippus intermontanus? Merriam. M 1 and M 2 , no. 21409, 

 natural size. Barstow Miocene, Mohave Desert, California. 



Fig. 42. Merychippus sumani? Merriam. P 2 to P 4 , no. 21402, natural size. 

 Barstow Miocene, Mohave Desert, California. 



Fig. 43. Merychippus calamarius stylodontus, n. var. Type specimen, M 2 

 and M 3 , no. 21410, natural size. Barstow Miocene, Mohave Desert, California. 



Fig. 44. Merychippus calamarius stylodontus, n. var. P 2 and P 3 , no. 22474, 

 natural size. Barstow Miocene, Mohave Desert, California. 



The M . sumani group comprises specimens much smaller than those 

 referred to 31. c. stylodontus, but apparently neither absolutely nor 

 relatively shorter crowned. The enamel bordering the fossettes is 

 commonly more complicated than in any of the larger Merychippus 

 specimens of the Barstow. 



The M. c. stylodontus form corresponds most nearly to Cope's 

 type specimen of M. calamarius in dimensions and in proportions of 

 the upper cheek-teeth in cross-section, but differs from the typical 



