THE PINEAL SYSTEM OF FISHES 



201 



in the pineal gland or epiphysis of birds and mammals. The general 

 impression is that of a vestigial structure, any variations of which, such as 

 are present in different types of living fish, being chiefly accountable on 



p.mx 



supr. oc." 

 f. moqrr 



LiL_V-p.f 



w par 



sz~ — ex oc 



~-- oc cond. 



Fig. 141. — The Parietal or Pineal Plate of Lacerta agilis and of Pleura- 

 canthus, a Primitive Type of Fossil Fish belonging to the Carboni- 

 ferous and Permian era. In Lacerta a Parietal Foramen and Parietal 

 Sense-organ are still present. In the Extinct Pleuracanthus the 

 Parietal Foramen had already disappeared. 



Lacerta agilis. (After W. K. Parker.) 

 ex. oc. : exoccipital. 

 ext. nar. : external nares. 

 /. magn. : foramen magnum. 

 jr. : frontal. 

 max. : maxilla. 

 nas. : nasal. 

 oc. cond. : occipital condyle. 



par. : parietal. 

 p. mx. : praemaxilla. 

 p.f. : parietal foramen. 

 pp. : pineal plate. 

 pr.fr. : praefrontal. 

 s. orb. : supraorbitals. 

 supr. oc. : supraoccipital. 



B : Pleuracanthus. Dermal bones of the head seen from above. (After Davies.) 

 mx. : maxilla. pp. {Jr.): pineal plate, probably repre- 



nas. : nasal. 



orb. c. : orbital cavity. 



par. : parietal. 



po. : postorbital. 



senting fused frontals. 

 sp. oc. : supra-occipital. 

 sq. : squamosal. 

 st. : supratemporal. 

 tb. : tabular. 



