No. 2.] THE RELATIONS OF PROTOCERAS. 31 1 



vermis of the cerebellum ; laterally they become concave, so 

 as to enclose a deep fossa on each side. The paroccipital 

 processes are long, slender and laterally compressed ; in shape 

 and relative position, they are quite like those of MoscJms. 

 The inferior surface of the exoccipital, between the paroccipital 

 and the condyle, is not wide, but is unusually long in the fore 

 and aft direction ; this space is not bounded in front by a ridge 

 running from the paroccipital to the basioccipital, as is the 

 case in many deer. The foramen magnum is rather small and 

 of subcircular shape ; its dorsal border is notched in the mid- 

 dle line and on each side of the notch is a more or less promi- 

 nent and thickened process. The supraoccipital is high, but 

 narrow and very thick, especially in the upper portion, where 

 the diploetic structure is well developed. The posterior sur- 

 face is concave and small "wings" are formed on the sides. 

 The parietals do not take part in the formation of these wings, 

 because the supraoccipital is reflected over upon the top of the 

 skull and forms an appreciable part of the cranial roof, not 

 only in the middle line, as in MoscJms, but also upon the sides, 

 as in the tragulines. The summit of the lambdoidal crest is 

 formed entirely by the supraoccipital. None of the existing 

 Pecora has such a primitive type of occiput as Protoceras. In 

 all of them the occiput is much lower and broader ; there are 

 no such marked median convexity and deep lateral fossae, and 

 the crest is almost or entirely obliterated. Even the tragu- 

 lines have this region shaped more like that of the Pecora 

 than has Protoceras. On the other hand, the shape found in 

 the latter occurs also in many ancient artiodactyls, such as the 

 oreodonts, but in this family the occipital wings are much 

 more prominent and the parietals take part in the formation 

 of them. The Deep River genus, Blastovieryx, which is an 

 undoubted member of the Pecora, has an occiput strangely like 

 that of the oreodonts. 



The cranium, which is remarkably well-rounded and capa- 

 cious for a White River animal, though not very large, judged 

 by the modern standard, is roofed in principally by the large 

 parietals, which cover nearly the whole cerebral fossa and extend 

 farther forward than in the existing Pecora, though the parietal 



