PARAHIPPUS. 



83 



Parahippus coloradensis praecurrens subsp. nov. 

 Plates 8.1, 9.1, 36.2,3. Text Fig. 58. 



Horizon and locality. — Upper Rosebud formation, Shannon County, South Dakota, Merycochoerus zone. Type 

 collected by Thomson, American Museum expedition of 1906. 



Type. — Amer. Mus. 1301S. Upper grinding teeth, p 2 -m 3 , and hind foot. Paratypc. Amer. Mus. 12925. A lower 

 jaw fragment with premolars, parts of tibia and radius, fore foot and both hind feet. 



Type figure. — Plate 9.1, text Fig. 58 of this Memoir. 



Characters. — (Matthew 1913, Osborn 1918) (1) Size of Parahippus te.vanus, one-eighth smaller than P. nebrascensis. 



Paraki.ppus coloradeNSis praecurreNS 



Fig. 58. Parahippus coloradensis praecurrens Osborn. (Upper) Left superior premolar-molar series of type, Am. 

 Mus. 13018, crown view. (Lower) Left inferior premolars (pi-4) of Amer. Mus. 12925, paratype, crown view. Both 

 figures natural size. 



(2) Crochet absent on p 2 , strong on p 3 -m 3 ; (3) pi and probably p 1 relatively large, compressed, pi with distinct heel; (4) 

 metastylids imperfectly separated from metaconids. (5) Limbs and feet relatively slender, with (6) lateral metapodials 

 greatly reduced. 



In the hypsodontism of its grinding teeth this animal is allied to the type of P. coloradensis Gidley, but is distinguished 

 (1) by the greater separation of the metastylids, especially on po, and (2) by the relatively small size of P2. The cotype 

 lower jaw indicates an animal slightly smaller in size than the type of P. nebrascensis, with teeth narrower and more hypso- 

 dont, external cingula incomplete, pi more elongate and having a distinct heel. The limbs are slender and the feet are 

 long, with the lateral digits greatly reduced. The radius is actually longer than in any Hipparion and much longer 

 than that of any Mcryehi ppus; the ulna is separate throughout. The fore feet are proportioned as in H. whitneyi but 

 only seven-eighths as large. Mtc. V is a diminutive nodule. The pes is long and slender like that of H. whitneyi but 

 only three-fourths as large; the lateral digits are reduced to very slender, thread-like splints; the phalanges are shaped 

 like those of Hipparion and Mcrychippus. 



