40 



OSBORN: OLIGOCENE, MIOCENE, PLIOCENE EQUIDiE. 



Type. — Amer. Mus. Nat. Hist. 9662, dp 2 4 , m 1 . Measurements: m 1 a.p. .0105, tr. .014. Cotypcs. Dp 2 4 (Amer. 

 Mus. Nat. Hist. 9661), p-m 1 (Amer. Mus. Nat. Hist. 9663). 

 Type figure — Plate 2.1, text Fig. 20 of this Memoir. 



Characters. — (Osborn, 1904, p. 170)" Distinguished from M. celer by full size of m 3 ; from M. westoni by sharp 

 elevation of crests and absence of internal cingulum; from M. latidcns by smaller parastyle and sub-equal length of proto- 



Fig. 20. Type of Mesohippus montanensis Osborn, Amer. Mus. 9662, dp M , m 1 . Natural size. Reversed in drawing. 



loph and metaloph. Molars more quadrate in form than in M. latidens. Protoconule quite distinct in protoloph; meta- 

 conule well defined on base of metaloph. Hypostyle absent or extremely rudimentary. A fore foot associated with a 

 single m 3 of the same species exhibits a large splint of Mtc. v." 



Mesohippus portentus sp. nov., Douglass, Earl. "XV. Fossil Horses from North Dakota and Montana," Ann. Carnegie Mus., 

 Vol. IV, Nos. Ill, IV, Apr. 1, 1908, pp. 268-269, PI. Ixv, type, figs. 2, 3, paratypes, figs. 1, 4. 



Horizon and Locality. — Type and paratypes from " Lower White River (' Titanotherium') beds, Pipestone Creek, 

 near Whitehall, Montana." Type collected by Earl Douglass. 



Type. — Carnegie Mus. 1622, a second right upper molar. Measurements: " Antero-posterior diameter of crown 

 13.3 mm., transverse diameter 18 mm., length of protoloph 12.2 mm., length of metaloph 12 mm., height of hypocone 



Fig. 21. Original figures of type and paratypes of Mesohippus portentus Douglass. Type (2, 3), Carnegie Mus. 1622, 

 m 2 of the right side; paratypes (1), Carnegie Mus. 1633, two lower molars, and (4) Carnegie Mus. 1623, a left m 3 . Greatly 

 enlarged. After Douglass, 1908, PI. Ixv, figs. 1-4. 



8.1 mm." Paratypes. A left upper premolar (Carn. Mus. 1624), a left m 3 (Cam. Mus. 1623), two lower molars (Cam. 

 Mus. 1633), a lower molar (Carn. Mus. 1634). 

 Type figure. — Text Fig. 21 of this Memoir. 



Characters. — (Douglass, 1908) " (1) Size large and (2) crests of molars high for a horse from this horizon, (3) ecto- 

 loph very oblique, (4) protoloph and metaloph nearly equal in length, (5) protoloph large and connected with the para- 



Mesohippus montanensis 



Mesohippus portentus Douglass, 1908. 



Text Fig. 21. 



