110 MAMMALIAN ANATOMY 



the head and medially, meeting its fellow in the middle line ventral to 

 the caudal border of the ventral surface of the preceding vertebra. 

 This ossicle represents a limb of the small V-shaped ha3mal arch, 

 known as a chevron bone, which is best developed in the first few 

 caudal vertebrae and is never developed in any other region of the 

 spinal column. 



TYPE OF THE PROXIMAL CAUDAL VERTEBRA. 



The Fourth Caudal Vertebra (Figs. 79, 81) closely resembles the 

 last sacral, but differs from it in being free, narrower, and longer. The 

 spinous process is absent or represented by a low median ridge. 



The body is longer than the neural arch, which is complete and 

 encloses a small triangular neural canal. The pedicles slope medially 

 and dorsally, and the laminae are almost horizontal. The transverse 

 processes are not prolonged toward the sacrum, but have a caudal 

 and lateral direction and extend far beyond the ends of the caudal 

 articular processes. Their tips are usually slightly bifid. 



The cephalic articular processes are large, and each shows a trace 

 of a mammillary process. They are separated by a deep median 

 ernargination in the cephalic border of the neural arch. The cephalic 

 articular surfaces face in a medial and dorsal direction. 



The caudal articular processes are distinct and horizontal, and the 

 articular surfaces face ventrally and laterally. 



The chevron bone is a small but well-developed arch, and articu- 

 lates with tubercles on the cephalic end of the ventral surface of the 

 body. 



TYPE OF THE TERMINAL CAUDAL VERTEBRA. 



The Sixteenth Caudal Vertebra (Figs. 79, 81) is slender, and so 

 greatly elongated that the length is ten or twelve times the width. 

 The reduction of the processes which was begun in the eighth has 

 been here almost completed ; the processes are represented by traces 

 of one caudal dorsal, two cephalic dorsal, two lateral, and two cephalic 

 ventral tubercles. 



DETERMINATION OF CAUDAL VERTEBRAE. 



This determination is not difficult when we are examining the bones 

 taken from one specimen. There is a gradual increase in width and 



