Reviews — Prof. 0. C. Marsh's Dinocerata. 



223 



and complexity of the brain from Eocene times to the present period 

 in the Mammalia. 



The Vertebrce. — The cervical vertebrse of the Dinocerata in their 

 main characters resemble those of the Proboscidians. The atlas and 

 axis are somewhat similar to those of the Elephant. The rest of the 

 cervicals (Figs. 12 and 13) are proportionally longer. The entire 

 neck was about one-third longer than in the Elephant, thus rendering 

 a proboscis unnecessary, as the head could readily reach the ground. 

 All the prsesacral vertebra, behind the atlas and axis, have the 

 articular faces of the centra nearly flat, as in the typical Proboscidians. 



Fig. 12.— Cervical vertebra of Tinoceras grande. Fig. 13.— Side view of the 



Marsh ; front view, one-fourth natural size, nc, same vertebra. Letters as in 



neural canal ; z, anterior zygapophysis ; /, lateral Fig. 12. 

 foramen ; z', posterior zygapophysis. 



"The trunk- vertebra in i\Q Dinocerata are proportionally longer 

 than those in the cervical region. The articular faces of the centra 

 are likewise nearly flat, most of them being distinctly concave 

 (Figs. 14 and 15). 



Fig. 14.— Front view of second dorsal vertebra of Fig. 15.— Side view of 



Dinnceras mirabile, Marsh, n, neural canal ; s, neural the same vertebra, 



spine; z', posterior zygapophysis. 



The Fore-limhs. — The limb-bones in the Dinocerata are nearly or 

 quite solid, and this is true of all the skeleton, a portion of the skull 



