SYi\OPSI8. 199 



Diiioccras distaiis, Marsh. 



Woodcuts: 4, p. 13; 8, p. 15; 10, p. 16; 31, p. 29. 



Marsh, Fiftli Annual Report U. S. Geological Survey (figures from the present volume, 

 viz :) fig. 41, p. 25S; 45, p. 260; 66, p. 270, 1884. 



The skull in the type specimen of this species (number \2l\!')) has 

 nearly tlie same g-eneral shape as in the type of Dinoccras mirahile, but is 

 somewliat more robust, tliouyh pertaining- to a young animal, as shown by 

 the general!}" ojien sutures. The nasals taper in front, and bear a pair of 

 low rounded oblicpie tul)ercles, much as in number 1036. They are 

 terminated, as in that specimen, by flattened, nearly vei'tical, and deei)ly 

 pitted, sutiu-al surfaces, from which the prenasals have fallen away. 



The maxillary elevations are stout and conical, and are connected 

 across the median line of the skull by an elevated ridge. The naso- 

 maxillary suture curves inward between the maxillary protuberances, and 

 is strongly marked on their inner surfaces. 



Beliind the maxillary protuberances, the top of the skull is flattened, 

 and jiresents two low oblique ridges, converging behind, along the lines of 

 tlie frouto-nasal sutures. At the sides, the superior surface is separated 

 from the lateral by a ridge, which rises nearly to the top of the parietal 

 jn-otuberances. Tiiese are well developed, triangular in section, and 

 directed upward and outward, and are situated above the post-glenoid 

 processes. The foramen magnum is below the upper margin of the 

 occipital condyles. 



In the type specimen, the post-glenoid process is robust. Tlie 

 zygomatic process of the squamosal is deeply excavated in front of the 

 glenoid cavity, for the posterior end of the malar bone, which is 

 peculiarly blunt, and rounded behind. Tlie palato-maxillary foramen is 

 rounded, and placed o^jposite the posterior half of the first premolar. 



The cavity for the brain is exposed in this specimen, and shows a 

 nasal septum just in front of the anterior constriction. The short olfactory 

 lobes were bounded in front by thin cribriform plates. 



The young specimen (number 1601) agrees with the type (numljer 

 1235) in the general shape of the skull, in the form of the maxillary 

 protuberances and connecting ridge, in the shape, and position of the 

 parietal protuberances, and in the j^osition of the palato-maxillary foramen. 

 Also in the deep excavation for the end of the malar bone. The known 

 diflerences may be attributed to age. 



The type of this species (number 1235) was collected by Mr. S. Smith, 

 in 1874, near Lone Tree, on Henry's Fork, Wyoming. 



The second specimen (number 1601) Avas found by Mr. Smith in 1882, 

 near Haystack Mountain, Wyoming. 



The geological horizoa of this species is in the Dinoceras beds. 



The type specimen of this sjiecies is j)reserved in the Yale Museum. 



