86 ODONTOKNTTHES. 



Measurements of Terminal Caudal Vertebral. (No. 1200.) 



Transverse diameter of anterior articulation of tenth caudal vertebra, 10.0 mm 



Vertical diameter of anterior articulation, 3.5 



Height of neural spine above floor of neural canal, 4.2 



Diameter of vertebra, across transverse processes, 48.0 



Antero-posterior extent of neural spine, 13.0 



Antero-posterior diameter of transverse process, at base, 8.0 



Antero-posterior extent on median line of the parts preserved of tenth and 



following vertebra, 25.0 



Diameter of the part preserved of eleventh vertebra, across transverse 



processes, 27. 



The last six or seven vertebrae in the tail of Hesperomis regalis were 

 so interlocked by the expanded transverse processes, as shown in figure 23, 

 below, that very little lateral motion was possible. The hypapophyses, 

 also, of the last two free caudals, would restrict vertical flexure materially, 

 so that the end of the tail would move mainly as a whole. This would 

 give great power, similar to that in the Beaver's tail, or in the flexible 

 blade of an oar. 





Figure 23. — Caudal vertebras of Besperornis regalis, Marsli ; seen from above, in position ; two-thirds natural 

 size. a. anterior convex face of first caudal ; I. transverse process of fifth caudal ; c. transverse process 

 of eleventh caudal, or middle vertebra of the pygostyle. 



