48 



COMPARATIVE DENTAL ANATOMY 



are found in many fishes and reptiles. There are 

 three forms of ankylosed teeth : Acrodont, Pleuro- 

 dont and Thecodont. 



In the acrodont tooth, a pedestal of bone de- 

 velops to support the tooth. During the process 

 of development, the tooth is developed in the 

 thecal fold and moved into position on the ridge 



Fig. 11. — Radiograph of head of Pickerel, showing acrodont ankylosis. 

 (By Dr. E. H. Skinner.) 



of the jaw. After the tooth is well in position, 

 the bone develops to support the tooth. When 

 the tooth is lost the bony support is lost also 

 (Fig. 11). 



The pleurodont tooth is attached to the side of 

 the bone and may get directly above the ridge of 

 the jaw. The top of the tooth projects above the 



