134 



PEOF. OWEN ON THE HOMOLOGY 



tiguous opening in the bony cranial roof in a proportion of the 

 class, which proportion is greater in the extinct members*. This 

 "pineal " production perforates, as a rule, the parietal bone, but 

 in some species the suture between that bone and the frontal, 

 rarely the frontal bone itself, and then near the suture, always 

 opposite the interval between the fore and mid brains. Beyond 

 this hole, commonly called " foramen parietale," but which may 

 preferably be termed "foramen pineale, " the upward continua- 

 tion of the conario-hypophysial tract or tube (fig. 1, 7, s) is closed by 

 the scalp or supracranial integument. 



In the class of Fishes the relative magnitude and tubular cha- 

 racter of this trans-cerebral tract is still more marked, examples 

 of which 1 have elsewhere described and figured f. In the Skate 



9 ^^ 



^ ^ iO' 



8 ^8' 



Section of cranium and brain of young Iguana, showing foramen parietale &c. 

 — 1. Neural axis. 2. Vertebral column. 3. Cerebellum, 4. Optic lobe. 

 5. Thalamencephalon. 6. Cerebrum. 7. Pineal body, 8. Pituitary body — 

 conario-bypoj)bysial tract (including " infundibulum " and "third ventricle"); 

 8' indicates the "protopharynx" of the embryo. 9. Mouth. 10. GuUet. 



* See ' Monograph on Ichthyo'pterygia'; Palteontographical Society's volume 

 for 1881, 4to, p. 94, pi. xxiii. fig. 1,/; also " Descriptive and Illustrated Cata- 

 logue of the Fossil Eeptilia of South Africa in the British Museum," showing 

 the parietal or "pineal" foramen in the genera Galesaurus, Petrophryne, Dicy- 

 oiodon, PtychognatJms, Oiidenodon, Kistecephalus, and Procoloplion : in some of 

 these genera the hole is unusually large. 



t 'Anatomy of Vertebrates/ 8vo, vol. i. 1866, p. 277. " The third ventricle in 

 Osseous Fishes is prolonged downward into the pedicle of the hypophysis or 

 'pituitary gland,' fig. 185, f, and upward into that of the conarium or 

 ' pineal gland,' fig. 175, w. The true vasculo-membranous infundibuliform 

 downward prolongation of the third ventricle exists in all Osseous Fishes. The 

 'infundibulum' is commonly short and thick, so that the hypophysis is almost 

 sessile, as in the Cod ; but in the Lophius the infundibulum is longer than the 

 entire brain, and the hypophysis lies at the fore part of the cranial cavity far 



