1889.] 4oD [Cope. 



and relatively smaller transverse diameter. Its dimensions are about 

 tlicise of the U. speciosiim, but it difTers from that species in the larger and 

 flatter inner column, longer crown, and less complex folds of the borders 

 of the lakes. 



Ths crown is long and nearly straight, as in H. occidentale. In its 

 present condition there is but little external cementum, which may be a 

 result of weathering, nevertheless that which remains in the grooves of 

 the inner side does not form a thick layer. The outlines of the lakes are 

 not extended inwards as in H. occidentale, and the transverse diameter of 

 the latter is relatively small. The anterior lake has one posterior inflec- 

 tion, one interior and one anterior ; of the posterior lake there are two an- 

 terior, none interior and one posterior ; a short loop extends towards the 

 inner column area. The latter is convex on the outer side, and without' 

 trace of angle or apex. 



Measurements. 



M. 



Length of crown 043 



-Tk- „ ►„..„ «f „>^„,„ (anteroposterior 021 



Diameters of crown \ ' 



( transverse 019 



Discovered by J. L. Wortman on Cottonwood creek. Eastern Oregon. 



HipPOTHERiuM MONTEZUMA Leidy. 



Proceedings Academy Philadelphia, 1882, p. 297. H. recfidens Cope, 

 Proceedings American Philosophical Society, 1886, p. 3G0. 



This species is known from two superior molar teeth, one of which is in 

 the possession of Dr. Joseph Leidy, and the other is in my private cab- 

 inet. It is nearly allied to the JB. occidentale, but is smaller, and the en- 

 amel borders of the lakes are rather more complex. The internal column 

 is longitudinal in section, and the internal face is slightly concave. The 

 posterior column is quite small, and is well defined from the posterior 

 inner crescent by a deep posterior sinus. Two strong loops project to- 

 wards the internal column from the adjacent enamel border. The lakes 

 have a deep emargination on each of their distant enamel borders, and a 

 number of loops on their approximated borders. One of these, which 

 represents the largest excurrent loop of other species, is of unusual size 

 and prominence, and is nearly isolated by the constriction of its isthmus. 

 In my specimen it is touched by the apex of an excurrent loop of the pos- 

 terior lake : in Dr. Leidy's, it can be traced lo a connection with the an- 

 terior lake, which is probably the normal relation. Lakes not much 

 expanded transversely to the crown. 



The crowns of both specimens are prismatic. That of mine is nearly 

 straight ; Dr. Leidy's is slightly curved, but not so much so as in the H. 

 petiinsulatum. 



