MERYCHIPPUS. 117 



Characters.— (Matthew, 1913) (1) Metastylid not separate on p 2 ; (2) metaconid-metastylid pillar forming a narrow 

 column, prominent but imperfectly divided; (3) heel of m 3 small, simple, somewhat broader below; (4) antorbital region 

 rather long, diastema one-third of the length of the grinding tooth row, symphysis mandibuli narrow, rather shallow but 

 incisive row rounded; (5) shaft of ulna very slender, reduced almost to a thread but imperfectly united proximally and 

 separate in distal half; (6) metapodials long and slender, lateral digits much reduced. 



A/o 93 9 7 Type 

 A . M. 



KlerycKippus eoplacidus 



Fig. 90. Merychippus eoplacidus Osborn, Amer. Mus. 9397, left lower grinding teeth of the type. Natural size. 



Merychippus proparvulus sp. nov. 



Plates 11.3, 15.6,7, 20.3, 54.1. Text Fig. 91. 



Horizon and locality. — Pawnee Creek beds, Pawnee Buttes, northeastern Colorado. Middle Miocene. Type col- 

 lected by F. B. Loomis of the American Museum expedition of 1901. 



Type. — Amer. Mus. 9394. Upper jaws, vertebra?, hind foot, and parts of limb bones; teeth much worn. 

 Paratypc. — Amer. Mus. 9398, a lower jaw, associated with two upper molars, moderately worn. Middle Miocene. 

 Type figure. — Plates 11.3, 15.6, 54.1, text Fig. 91 of this Memoir. 



Characters. — (Matthew, 1913) (1) Size medium. (2) Protocone strongly united with protoconule in an early stage 

 of wear; (3) prefossette open until the tooth is deeply worn, the crochet uniting with metaconule only toward the base; 

 (4) fossette borders nearly simple (?) due to extreme wear; (5) absence of pli caballin (?) due to extreme wear; (6) meta- 

 conid-metastylid pillars forming a narrow column indistinctly divided by shallow groove; (7) nij large, heel of 1113 simple, 

 elongate. (8) No malar fossa. (9) Ulnar shaft rather heavy, in proximal part at least united with radius one-third down, 

 distal half unknown; (10) metatarsals long, shafts of lateral digits moderately reduced; (11) ungual phalanges rather 

 narrow. 



Merychippus eohipparion sp. nov. 

 Plates 20.2, 44.3, 47.3, 49.3, 50.4,8, 54.3. Text Fig. 92. 



Horizon ami locality. — Pawnee Creek beds, Pawnee Buttes, northeastern Colorado. Middle Miocene. Type col- 

 lected by Barnum Brown of the American Museum expedition of 1901. 



Type. — Amer. Mus. 9402. Lower jaws, fore and hind limbs and feet, and several vertebrae, all belonging to a single 

 individual. 



Type figure— Plates 20.2, 44.3, 47.3, 49.3, 50.4,8, 54.3, text Fig. 92 of this Memoir. 



Characters. — (Matthew, 1913) (1) Metaconid well separated from metastylid on p 2 ; (2) metaconid-metastylid pillars 

 widely separated, deeply grooved in upper part of crown, flattening out at base of crown; (3) outer surface of protoconid 

 and metaconid not flattened; (4) anterior eingulum forming a prominent plate externally on lower half of tooth, wanting 



