DINOCERATA. 589 



2. Species of intermediate size. 



Molars smaller, with an additional tubercle on the last U. robustum. 



Last molar without additional tubercle; maxillary horn-cores 

 low, triangular; posterior horn-cores short, triangular in sec- 

 tion (Marsh) U. miraUle. 



3. Smallest species (occipital condyles extending over about M. 0.95). 



Molar teeth larger, the last with a posterior exijansion U. lacustre. 



UlNTATHEEIbM KOBUSTUM, Leidy. 



Proceed. Acad. Nat. Sci., Phila., 1872, p. 109, August. Report U. S. Geol. Surv. Terrs., i, pp. 96, 333, 

 pi. XXV, tigs. G-l"2; iil. xxvi, figs. 1-3; pi. xxvii, figs. 30-34. Vintamastix atrox, Leidy, /. c. 



I have been able to examine, through the kindness of Professor Leidy, 

 the type of his description, and find it to belong to a smaller species than 

 any of those above described. The lateral-parietal and supra-occipital 

 crests are well developed, and the lattQr extends obliquel}^ backward. Sev- 

 eral peculiarities are to be observed in the dentition. Thus there is a great 

 inequality in the height of the transverse crests of the posterior upper 

 molar, the anterior, or the arched one, rising to a high cusp at its outer 

 extremity. A small tubercle exists on the side of the inner angle of the 

 grinding surface in the penultimate molar. The same angle is much ele- 

 vated in an anterior molar. The canine is wider distally than in L. cornutus 

 and less recurved. The mastoid process is quite prominent. The humerus 

 has a prominent internal condyloid ridge and tuberosity, and the condyles 

 are not very oblique. The inner posterior lobe of the tibial face of the 

 astragalus is quite well defined. There is no median ligamentous pit on 



the trochlear face. 



Measurements (from Leidy). 



Inches. 



Depth of lower jaw at last molar 3.25 



Length of humerus, about 21. 00 



Diameter at condyles 7.50 



I obtained a fragmentary lower jaw of this species from Henry's Fork 

 of Green River in 1873 One ramus contains the roots of six posterior 

 molars; the other sustains large portions of the crowns of the last two. 

 The latter agree with the corresponding teeth as figured and described by 

 Leidy. I have represented them on Plate XXXVI, Fig. 2. The sym- 

 physis of this mandible is preserved, and is represented on Fig. 1 of the 

 same plate. It is of singular form, being solidly coossified and very much 

 compressed.' Its inferior middle line is an obtuse keel, which rises ante 



