1903.] Matthew, Fauna of Titajwtherium Beds of Montana. 223 



zon, and agrees well enough with other first molars in our 

 series. The character by which Cope separated it from L. 

 evansi, the absence of . _ , 



defining furrows to 

 the rib of the external 

 crescents, is exhibited 

 only on first molars, 

 and not on all of 



tneSe J out two Otner Fig. 15. Leptomeryx esuUatus. Lower jaw, natural 



1 , p . size, external view, composite, Nos. 0606, 0706, 0702. 



characters of more im- 

 portance are seen in our material, viz.: 



1. The median internal cusp, a strong cusp in m3 of L. 

 evansi, and a smaller one on m^ and m^ is quite small on m3, 

 and absent, or nearly so, on m^ and m^ 



2. In the third lower premolar the protoconid has two pos- 

 terior ridges, of which the internal one connects with the heel, 

 and the external one does not; while in L. evansi and other 

 species from the Oreodon and Leptauchenia Beds, the exter- 

 nal ridge connects with the heel, and the internal one does 

 not. 



In the lower jaw I have observed no entirely constant dis- 

 tinctions, except in P3. The first premolar is small, and is 

 separated from p2 by a diastema of about the same length as 

 that of L. evansi; the size of the jaws averages larger than 

 those of L. evansi from South Dakota, and all are larger than 

 L. evansi of Colorado. The height of crowns and proportion 

 of the teeth are about the same, and the premolar pattern, 

 allowing for individual variation, is identical, except as above 

 noted. 



I have no doubt that better material will furnish more sat- 

 isfactory distinctions, but, except for the characters noted 

 above, I am unable to find any in the teeth. 



Measurem e nts . 



Lower premolars p2_4 19 mm. 



Lower molars rtii-j 24 



Upper molar, m3 , antero-posterior 8. 



" transverse 8.5 



