82 ODOXTORNITHES. 



A small free hypapophysis was articulated with the posterior lower 

 margin of this vertebra, and also with the adjoining margin of the succeed- 

 ing centrum. This bone resembles somewhat the corresponding- part in the 

 Loon, and is clearly homologous with the chevron bones in reptiles. The 

 neural arch of the fifth caudal extends over nearly the whole centrum. 

 The posterior margin of the spine curves backward above the neural canal, 

 and the s umm it of the spine is directed forward. The neural canal is 

 materially smaller than in the fourth vertebra, but is similar in outline. 



Measurements of Fifth Caudal Vertebra. (No. 1200.) 



Length of centrum, 13.0 mm 



Transverse diameter of anterior articulation, 11.0 



Vertical diameters of anterior articulation, 9.0-10.2 



Transverse diameter of posterior articulation, 11.0 



Vertical diameters of posterior articulation, 9.0- 9.5 



Length of floor of neural canal, 12.0 



Length of roof of neural canal, . 9.5 



Transverse diameter of neural canal, at anterior opening, 3.2 



Vertical diameter of neural canal, at anterior opening, 4.0 



Transverse diameter of neural canal, at posterior opening, 4.0 



Vertical diameter of neural canal, at posterior opening, 4.0 



Diameter of vertebra, across transverse processes, 39.0 



Antero-posterior diameter of transverse process, at base, 1.0 



The Sixth Caudal Vertebra. (Plate XII, figure 6.) 



This vertebra differs considerably from the fifth. Its centrum is long-er, 

 and much more slender. The transverse processes are much longer, and 

 so expanded at their distal ends as to greatly restrict lateral motion ; which 

 was still further prevented by the same means in the succeeding vertebrae. 

 The under surfaces of the transverse processes have a marked prominence 

 at the point where the outward bend occurs. These prominences extend 

 below the ventral surface of the centrum. A free hypapophysis, very 

 similar to the one already described, articulated with the posterior margin 

 of tins vertebra also. The neural arch is mainly upon the anterior half of 

 the centrum. The neural canal is small, and triangular in outline, and the 

 neural spine is of moderate height. 



