334 SCOTT. [Vol. XI. 



the first lumbar, much longer on the second and reaches its 

 maximum length on the third, while the overlapping ilium pre- 

 vents its attaining any great length on the fifth. 



No Sacral and but one Caudal Vertebra is preserved in any 

 of the specimens. The latter belongs to the proximal part of 

 the tail and has a relatively large subcylindrical centrum, which 

 indicates that Protoceras had a much better developed tail than 

 Moschus or than the modern deer generally, and which was 

 comparable in proportionate length to that of the giraffe. The 

 prezygapophyses are very long, but do not appear to articulate 

 with any other vertebra. The specimen belongs to a younger 

 and somewhat smaller animal than the skeleton here described 

 and both epiphyses are lost. This fact must be allowed for in 

 using the measurements given below. 



The Ribs. — In many primitive artiodactyls, such as Oreodoji, 

 the ribs are notably slender and subcylindrical, resembling those 

 of the carnivores. In Protoceras they are entirely pecoran and 

 resemble those of MoscJms in general, but their somewhat greater 

 length and curvature and the increased distance between the 

 head and tubercle point to a wider and more capacious thorax. 

 The anterior ribs are short, subcylindrical proximally, expanded 

 and plate-like distally ; the maximum length is attained about 

 the middle of the thorax ; posteriorly the ribs become con- 

 tinually more slender and rounded, as well as shorter. 



Measurements. 



Protoceras. Moschus. 



Atlas, greatest length 0.050 m. 0.029 m. 



Atlas, greatest breadth 072 .036 



Axis, length of centrum 041 .035 



Axis, breadth of anterior face 032 .024 



Axis, length of odontoid process 013 



Sixth cervical, length of centrum 025 .025 



Sixth cervical, breadth of anterior face 013 



Seventh cervical, length of centrum 019 .016 



Seventh cervical, breadth of anterior face 013 



First thoracic, length of centrum 015 



First thoracic, breadth of anterior face 015 



Last thoracic, length of centrum 020 .022 



Last thoracic, breadth of anterior face 018 



First lumbar, length of centrum .022 .024 



Second lumbar, length of centrum 024 .024 



