222 



THE PINEAL ORGAN 



the skull. A more detailed description of the pineal region of Ceratodus 

 is given by Studnicka (1905), more especially with regard to the relation 

 of the pineal organ to the posterior wall of the dorsal sac, and of the end 

 vesicle which extends forward to and overlaps the paraphysis as in 

 Protopterus. 



Iab.r-.J- 



Fig. 156. — Dorsal View of Skull of Ceratodus Fosteri. (After Huxley.) 

 Investing bones, lightly stippled. Cartilage, dark stipple. 



am. : anterior median bone. 



art. : articular surface for 2nd fin ray. 



cr. : cartilaginous cranium. 



i.l. : inner lateral bone. 



lab. : labial cartilages. 



lam. : process covering lungs. 



ol. : outer lateral bone. 



op. : operculum. 



p.m. : posterior median bone. 



pr. orb. : preorbital. 



sb. orb. : suborbital. 



pin N h.g op 



pm x h.g. p.c 



par. v 



Fig. 157. — Sagittal Sections through Brain of Lepidosiren. Left : Early 

 Stage. Right : Detail of Later Stage of Development. (After J. Graham 

 Kerr.) 



ax. : anterior commissure. par. : paraphysis. 



ch. pi. : choroid plexus of lateral p.c. : posterior commissure. 



ventricle. pin. : pineal diverticulum. 



h.c. : habenular commissure. op. ch. : optic chiasma. 



h.g. : habenular ganglion. op. I. : optic lobe. 

 n. ch. : notochord. 



