LABYRINTIIODONTIA. 



351 



" The parietes of the teeth are deeply plaited and folded, so 

 as to give rise to a complicated 

 * labyrinthine ' pattern in the 

 transverse section of the tooth. ' ; 



The points in which the Laby- 

 rinthodonts differ from the mo- 

 dern Urodela are chiefly to be 

 found in the fact that the head 

 is defended by an external cov- 

 ering or helmet of hard and 

 polished osseous plates, in the 

 possession of ventral integument- 

 ary scutes, in the existence of 

 exoskeletal plates occupying the 

 place of the interclavicle and cla- 

 vicles, in the amphiccelous form 



Fig. 309. Foot-prints of a Labyrinthodont (CJuirotkerium), from the Trias. The 

 upper figure shows a single foot-print enlarged ; the lower figure shows a slab, with 

 several prints, and traversed by reticulated desiccation-cracks. 



