VASCULAR SUPPLY OF PINEAL SYSTEM OF SPHENODON 267 



and the anterior choroidal artery. The saccular artery gives off, on either 

 the left or the right side : (1) the anterior pineal artery, which goes to 

 the pineal eye ; and (2) the posterior pineal artery which supplies the 

 hinder part of the pineal sac. The anterior pineal artery in one case 

 described by Dendy arose directly from the posterior cerebral artery of 

 the left side. It was unpaired ; it passed upwards on the left side of 

 the pineal sac, where it was hidden in folds of its walls and gave off 

 branches to the sac ; it gave off a recurrent branch which passed to the 

 right and finally accompanied by the left pineal nerve it entered the 

 space between the inner and outer fibrous capsules of the pineal eye, where 

 it broke up into capillary vessels which ramified in the connective tissue, 

 but did not enter the eye itself. This fact is of considerable importance, 

 as it is unlikely that an organ which has no demonstrable blood supply 

 could be actively functional, and it indicates impending degeneration. 



The Parietal Foramen of Reptiles 



The parietal foramen is not present in all orders of the class Reptilia. 

 When present it is usually situated in the anterior part of the interparietal 

 suture. It is found in this position in Sphenodon (Fig. 189), which is the 



p. mx 



J U S 



sq. 



N cond. 

 Fig. 189. — Dorsal View of Skull of Sphenodon, showing the Parietal 



FORAMEN. 



cond. : condyle. p. mx. : premaxilla. 



ex. p. : external pterygoid. pa : parietal. 



jr. : frontal. pa. f. : parietal foramen. 



jug. : jugular. pr.f. •' prefrontal. 



mx. : maxilla. sq. : squamosal. 



na. : nasal. 



(From the Cambridge Natural History.) 



only living example of the Prosauria ; and it is present in the same 

 situation in Palceohatteria and in Conodectes, one of the most primitive 

 of the Permian reptiles. It is found also in the same site in the less 

 primitive mammal-like reptiles, the Therocephalia and in the Plesiosauria. 



