No. 2.] THE RELATIONS OF PROTOCERAS. 331 



The seventh cervical is the shortest of the series and has a 

 centrum of a shape differing from that of all the others ; it is 

 narrow in front and the anterior portion is so sharply con- 

 stricted that it appears to stand upon a short neck ; behind 

 this it immediately broadens and the posterior face is wide and 

 depressed and displays facets for the heads of the first pair of 

 ribs. The faces are still somewhat oblique in position. The 

 neural arch is very short, being cut away between the pre- 

 zygapophyses, as is also the case in the sixth vertebra, another 

 marked change in the direction taken by the spinal column 

 occurring at this point. The prezygapophyses are very large 

 and widely separated ; for most of their extent they face up- 

 ward, with but little obliquity, but the articular surface is re- 

 flected downward upon the inner side of the process and 

 presents inward. This accessory facet articulates with the 

 corresponding one on the outer side of the neural arch of the 

 sixth vertebra, which has already been described. The post- 

 zygapophyses are very small, hardly a third as large as the 

 anterior pair. The neural spine is no higher than that of the 

 sixth, but is much larger in every other dimension and looks 

 like a truncated thoracic spine, which stands erect, instead of 

 pointing forward as in the other cervicals. The transverse 

 process is quite a long, depressed bar, which, as usual, is im- 

 perforate. This vertebra differs from the corresponding one 

 of MoscJuis in the heavier neural spine, the much more decided 

 lateral projection of its zygapophyses and the longer transverse 

 processes. 



The Thoracic Vertebrce (PI. XXI, Fig. 8) were probably four- 

 teen in number. Their number cannot have been less than 

 twelve, since so many are preserved in a single specimen and 

 do not form an entirely unbroken series, and can hardly have 

 exceeded fourteen, because the same specimen has preserved 

 five lumbars, apparently the entire series. It is not impossible, 

 of course, that the typical artiodactyl formula of nineteen 

 thoraco-lumbar vertebrae was exceeded in this genus, but there 

 is no reason to assume that such was the case. 



The first thoracic has a short, broad, depressed and distinctly 

 opisthocoelous centrum. The prezygapophyses are like those 



