354 MICROSCOPIC ANATOMY OF THE TEETH 



of the jaw, with which it is continuous. Both in its lamina- 

 tion and in the irregular lacunae and other spaces which it 

 exhibits it has a coarser appearance than the bone beneath. 

 It is well developed in the teeth of Ophidia. The fusion of 

 the teeth with the bone of attachment is often so complete 

 that it is difficult to distinguish tooth from bone, especially 

 in osteodentine teeth. 



(2) Attachment by an Elastic Hinge. A simple form of 



FIG. 234. Teeth of Eel showing union to bone of attachment, and 

 enamel tips. (Photographed from a specimen lent to the author by 

 Sir Charles Tomes. ) e. Enamel tips ; 6. bone of attachment. 



attachment by a hinge allowing of movement of the tooth 

 upon the bone of attachment is seen in the Echineis, the 

 sucking fish of the Shark, which attaches itself by a sucker 

 on the b?,ck of the head to the skin of the Shark, and although 

 also capable of free movement, obtains most of its nourish- 

 ment from the Crustacea and other organisms found in the 

 slimy substance on the shark's skin. 



The sucker allows of free movement of the fish in a for- 

 ward direction, but it cannot be detached backwards by 

 any force applied from the front. Each tooth is attached 

 to a special bone of attachment, but is not anchylosed to it ; 



