84 



DINOCERATA. 



The Median and Posterior Dorsal Vertebrae. 

 (Plate XXIV; and woodcuts 103-105, below.) 



In the dorsal vertebrti3 of Dinoceras, behind the third, the neural 

 s})ine gradually becomes shorter and weaker, and the neural canal, 

 ti-ansversely oval in outline.. Tlie transverse processes are more elevated, 

 and shorter. The centrum becomes more compressed below, so that 

 the articular faces are sub-triangular in outline, as shown in Plate 

 XXIV, figure 2. 



In the posterior dorsals, the neural spine is quite short, and weak. 

 The anterior zygapophyses have their articular faces recurved, as in the 

 nuninant mammals. The neural canal is a broad oval in transverse 

 outline. The transverse processes are much elevated, and the articular 

 faces for the ribs on these, and on the centrum below, gradually become 

 smaller. The centrum is longer, distinctly keeled below, and its articular 

 faces are triangular in outline, the three sides being nearly equal. These 

 features are shown in figures 103—105. 



The last dorsal vertebra of Dinoceras mirabile (number 1215) is 

 represented in I'late XXIV, figures 5-0. A posterior dorsal of another 

 species is shown below. 



Fig. 103. Fig. in-l. FiG. 105. 



Figure 103. — Posterior dorsal vertebra of Dinoceras lucare, Marsh (^fo. 1038); front view. 

 FlGDRE 104. — The same verlebra ; side view. 

 Figure 10 j. — The same vertebra ; back view. 



n. neural canal ; r. face for head of ril> ; )•'. face for tubercle of rib ; s, neural spine ; z. anterior 



zygapophyses ; z'. posterior zygnpophysis. 



All the flgiires are one-fourth natural size. 



