ORGANS OF SUPPORT, 



FIG. 31. 



bodies of the vertebrae occupy the same relative position 

 wherever there are anal fins developed between the tail 

 and the anus, as at a, J2. The inferior foramen of the 

 vertebrae, for the blood vessel is larger than that above 

 for the spinal chord, and it widens much in the pelvic 

 region (83,) in order to embrace the posterior parts of 

 the urinary and genital organs. The elements of the 

 cocygeal vertebras of fishes being thus extended upwards 

 and downwards, they present no transverse processes in 

 that region to impede the lateral motions of the tail, and 

 their nervous and vascular systems are here protected 

 from injury during the violent actions of that part of the body. 

 In the region of the abdomen the inferior interspinous 

 bones and the rays are placed at the ends of the trans- 

 verse processes, and extended more or less round the 

 viscera, as ribs (72,) which often present a bifurcated ap- 

 pearance by their sending a long process (73,) outwards 

 and backwards. The ribs are often merely minute epiphyses 

 at the ends of the transverse processes, as in the rays 

 and sharks, and they are continued forwards along the 

 vertebral column to the atlas ; so that there are no dis- 

 tinct free cervical vertebras. The bodies of the cranical 

 vertebrae continue along the floor of the cranium through 

 the basilar part of the occipital bone, the body of the 

 sphenoid, the ethmoid, and the vomer ; and these parts 

 are here extended forward in the same straight line with 

 the rest of the vertebral column. The ordinary concave 



