1918] Merriam: New Mammalia from the Idaho Formation 527 



The Idaho specimen is more slender than N. improvisus, and may 

 show slightly greater lateral compression. It is also more slender, 

 longer and more distinctly flattened transversely than horn-cores of 

 the Recent mountain goat, Oreamnos. Additional material will be re- 

 quired before the position of the species represented by this specimen 

 can be clearly determined. 



EQUUS IDAHOENSIS, n. sp. 



Type specimen, an upper cheek-tooth, no. 22348, from locality 3036C in beds 

 referred to the Idaho formation near Froman Ferry on the Snake Eiver, eight 

 miles southwest of Caldwell, Idaho. 



Referred to this species is also a lower premolar, no. 22347, from beds referred 

 to the Idaho formation at Froman Ferry. 



Cheek-teeth large and heavily cemented, characters as in typical Equus, 

 excepting in the nature of the protoeone of the upper cheek-teeth and of the 

 inner gutter between metaconid and metastylid columns of the lower cheek- 

 teeth. 



Protoeone very short anteroposterior^ but distinctly concave on the inner 

 border. Character of the protoeone approaching that of Equus stenonis of the 

 European Pliocene. Gutter on inner border of metaconid-metastylid column of 

 lower cheek-teeth narrow and angular as in Pliohippus. 



Fig. 3. Equus idahoensis, n. sp. P*, occlusal view. Type specimen, no. 22,348, 

 natural size. From beds referred to Idaho formation, near Froman Ferry, Snake 

 River, Idaho. 



An upper tooth, no. 22348, from locality 3036C in Idaho beds near 

 Froman Ferry on the Snake River represents an animal as large as 

 Equus pacificus or the largest individuals of E. occidcntalis. The 

 crown (fig. 3) is very heavily cemented. Unfortunately it has suffered 

 so much wear that the original length and curvature cannot be esti- 

 mated. The fossettes are very narrow, as might be expected at this 

 stage of wear, and show plications of such extent as to indicate that 

 considerable folding of the walls would be shown at an early or middle 

 stage of wear. The outer styles are strong. The outer walls of proto- 

 eone and paracone are much flattened. The protoeone is small and 



