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University of California Publications in Geology [Vol. 9 



This species resembles NeoJiipparion affine in its large size and in 

 the high degree of lateral compression of the protocone. The anterior 

 and posterior fossettes (fig. 1) are narrow transversely and the enamel 

 surrounding them shows comparatively few plications. NeoMpparion 

 gidleyi seems to be distinguished from N. affine by its narrow fossettes, 



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Fig. 1. NeoMpparion gidleyi, n. sp. W, no. 21382, type specimen, natural 

 size. Outer and occlusal views. Lawler Ranch, six miles east of Petaluma, 

 California. 



Fig. 2. NeoMpparion molle, n. sp. M 3 , no. 21370, type specimen, natural size. 

 Inner view and cross-section near base of distal third, s, point at which cross- 

 section is cut. Lower Jacalitos, Pliocene, North Coalinga region, California. 



wider protocone, and slightly larger size. The two species are evi- 

 dently closely related and seem to represent nearly the same stage of 

 evolution. 



Measurements of Type Specimen 



M 3 , anteroposterior diameter 26.7 mm. 



M 3 , greatest transverse diameter 20.6 



M 3 , anteroposterior diameter of protocone 18.7 



M 3 , greatest height of worn crown 55.5 



