No. 478] ODONTOPHORAL APPARATUS IN SYCOTYPUS 721 



over a pulley (Fig. 8, rim). Since the 

 shoe-shaped, the ribbon is 

 folded together as it passes 

 back over the cartilage, and 

 unfolded as it passes forward; 

 otherwise the animal would 

 rasp its own tissues. As it is, 

 the lateral teeth (Fig. IS, It.) 

 are turned in against each 

 other, so that as the lingual 

 ribbon passes back from the 

 head of the cartilage they are 

 thrown out of action. This is 

 a very important point in the 

 mechanism, and one which has 

 not been insisted upon. The 

 shape of the head of the carti- 

 lage is perfectly adapted for 

 this folding and unfolding of 

 the ribbon as it plays back- 

 ward and forward. 



The crrooved surfaces of the 



5 not straight but horse- 



an.i 



lOOtll 



moon-shaped. Muscles fi 

 place of attachment along 

 lateral edge, but the me( 

 «dge is thin and free of mi 



AH. 



attachment 

 vex side of each 



s alo 



rthc 



