54 FISH GALLERY, 



The series of bones constituting the axis of the body, and des- 

 tined to protect the spinal cord and some large longitudinal 

 blood-vessels, is called the vertebral or spinal column ; the single 

 bones are the vertebra. 



The vertebra consists of a body or centrum (fig. 41, c), with a 

 concave anterior and posterior surface, and of several processes or 



Fig. 41. 



Vertebra of Fish. 



apophyses, as : — 1. Two neurapophyses {na) which, on the dorsal 

 side, rising upwards, form the neural arch over the canal, in which j 

 the spinal cord is lodged. 2. Two joarapo/jAyses (pa), projecting 

 from the lower part of the sides of the body, or two heemapophyses 

 (ha), which coalesce to form on the ventral side the haemal canal 

 for a large trunk of the vascular system. ' 3. A neural spine (ns), 

 which crowns the neurapophyses. 4. A haemal spine (As), having i 

 the same relation to the hsemapophyses. 5. Two pleurapophyses 

 or floating ribs, suspended from the parapophyses. 6. Oblique! 

 articular processes, zygapophyses {sa), developed from the base of 

 each ncurapophysis. 



The vertebrae are divided into abdominal and caudal, the latter 

 distinguished by the coalescence of the parapophyses into a com- 

 plete haemal ring; the suspension of the anal fins forms the boundary 

 between the two divisions (fig. 37). The abdominal vertebrse^ 



