1889.] 4d7 [Cope. 



Hippodon speciosus Leidy. Proceed. Phila. Academy, 1854, p. 90. 



This species appears to have been pretty generally distributed over 

 Western North America, excepting the extreme Northwest. Among the 

 numerous specimens sent me from Montana and Oregon, I have not recog- 

 nized any as belonging to this animal. The species has been heretofore 

 known by teeth only, in spite of its relative abundance ; but my party in 

 Northern Kansas, under Mr. Hill, obtained an almost perfect cranium ac- 

 companied by three cervical, four dorsal and one lumbar vertebra,', and 

 part of the sacrum ; with parts of foreleg and foot and one-half the 

 pelvis. A superior molar of a second individual, from the same locality, 

 is accompanied by a mandible with teeth, and bones of various parts of 

 the skeleton. An opportunity for determining the general characters of 

 this horse is now first presented. 



Skull— fonn. — The cranium is about the size of that of the black-tailed 

 deer {^Gariacus macrotis). The profile of the ffont is nearly straight, with 

 a slight convexity in front of the infraorbital region. The latter is flat or 

 a little concave in both directions as far on each side as a line drawn ante- 

 riorly from the temporal fosste ; from these lines it slopes to the orbital 

 border, flat posteriorly, becoming convex anteriorly, strongly so above 

 the lachrymal bones. The profile of the parietal region descends steeply 

 to a point above the meatus auditorius exlernus, and rising again into 

 a prominent sagittal crest, joins the inion at the extremity of another 

 descending slope. The inion is somewhat truncated at the summit. The 

 anterior part of the sagittal crest is low, and divides at a very acute angle 

 above the middle of the glenoid cavity. The horizontal angle of the 

 malar and maxillary bones is prominent, extending forwards nearly to the 

 anterior part of the first true molar. The preorbital fossa is limited in ex- 

 tent, occupying a position above the infraorbital foramen. Its sides rise 

 gradually except on the upper border, which is abrupt. The muzzle is 

 not excavated anterior to the fossa, but the usual contraction of the border 

 of the diastema is strong. The acumination of the apices of the nasal 

 bones is on their inner sides, and extends as far forwards as the line of the 

 canine teeth. The notch of the nostrils extends to a point above the an- 

 terior border of the second (first large) premolar. 



The zygomata are slender and little expanded, they are compressed be- 

 hind. The orbital portion is triangular in section behind, with an external 

 and a superior plane. The orbit is large and a little deeper than wide, the 

 width equaling just one-fourth the distance from its posterior border to 

 the extremity of the nasal bone. The postfroatal process presents its 

 edge outwards and its broadsides directly fore and aft. The occipital 

 region is rather contracted above. Its superior half is occupied by a me- 

 dian keel. The paroccipital process is long, extending considerably below 

 the occipital condyles, and is compressed, presenting its sides outwards 

 and inwards. A narrow strip of the os petrosum is exposed between the 

 occipital and squamosal bones, extending as high up as the postinial fora- 



