THE PINEAL SYSTEM OF AMPHIBIA 237 



tendency for it to lessen in size or disappear in the more recent types and 

 living species indicate that the pineal organ itself was more highly evolved 



Pmx .. . Nar 



Fig. 170. — Dorsal View of Skull of Protriton, one of the Smaller Stego- 



cephala, Magnified. 



branchial arches. Nar. : nostril, 



frontal. P. : parietal. 



• parietal foramen. Pf. : prefrontal. 



maxilla. Sc. pi. : sclerotic plates. 



nasal. S. oc. : supraoccipital. 



(From Wiedersheim, after Fritsch.) 



Br. 



F. . 

 Fp. 

 M. 



N. 



Fig. 171. 



A — Dorsal aspect of skull of Procolophon (Seeley), a primitive reptile showing a 



large parietal foramen. 

 B — Cranium of Capitosaurus (Zittel), an extinct tailed amphibian belonging to the 



order Stegocephala, or labyrinthodonts, showing a parietal foramen. 



in the more ancient and primitive types, and has become vestigial in the 

 living representatives of these types, both in fishes and Amphibia. 



