496 GEOLOGICAL SUEVEY OF THE TEERITORIES. 



uninterrnpted. A short elevated fold proceeds from the latter, dividing 

 the head of the transverse valley. A compressed conic tubercle stands 

 between the inner extremities of the crests. The first premolar has two 

 transverse crests and an anterior tubercle. The j)osterior crest is 

 strongly curved backward at its inner end. A strong cingulum sur- 

 rounds the base of the crown except on the outer side. 



Measurements. 



M. 



Length of three anterior molars 0.090 



Length of third molar. 030 



Width of third molar 033 



Length of first molar 026 



Width of first molar 019 



ANCHITHERIUM, Kaup. 



Three species of this genus left their remains in considerable abun- 

 dance in the Miocene of Colorado. One of these is the A. hairdii, Leidy ; 

 a second is similar to, and a third smaller than, that well-known animal. 

 They are chiefly known from molar teeth, but greater or less portions of 

 the entire skeleton are frequently found. The following are some of the 

 characters by which the teeth may be recognized : 



I. Anterior median tubercle not separated from inner, obsolete on the 

 second premolar: 



A median ridge on each outer lobe, and basal tubercle between the 

 inner. — A. hairdii. 



II. Anterior median tubercle well separated from inner : 



Second premolar with anterior median tubercle distinct at both 



ends; no inner basal lobe.— -J., cuneatuni. 

 No inner basal lobes ; crescents with concave outer faces. — A. ex- 



oletum. 



These are the only species of horses known to occur in the Colorado 

 Miocene. 



Anchitheeium bairdii, Leidy, Ext. Fauna Dak. and IsTeb., p. 303, 



PI. XX. 



Not uncommon. 



Anchitheeium exoletum, Cope, spec. nov. 



Established on a portion of the right maxillary bone, which contains 

 the last premolar and first premolar in perfect preservation and part of 

 the third premolar. These teeth differ from the corresponding teeth in 

 A. bairdii in many respects, resembling in the constitution of their outer 

 lobes some of the symborodonts. The outer faces of these are uni- 

 formly concave to near the shoulder, leaving a very narrow basal ridge 

 and no longitudinal median ridges. The intercrescentic ridge is in- 

 curved and not straight. The anterior middle tubercle is separated 

 from the inner by a deep fissure and grooves to the base ; the median is, 

 on the other hand, continuous with the posterior inner. The posterior 

 median is very small. The anterior and posterior basal ridges are 

 small, and there is no trace of basal tubercle between the two medians. 

 Enamel smooth. 



The size of this animal was probably that of the A. hairdii, but the 

 molar teeth have the antero-posterior diameter greater in proportion to 

 the transverse than in that species. The foramen infraorbitale exterius 



