236 W. BALDWIN SPENCBB. 



PLATE XV. 



Fig. 7. — Longitudinal vertical section through the median line of the head 

 in Hatteria punctata in the region of the parietal foramen. Therelative 

 positions of the epiphysis, the pineal stalk, and pineal eye, are seen together 

 with the plug of connective tissue filling up the foramen. In front of the 

 epiphysis is the vascular roof of the thalamencephalon. 



Fig. 8. — Diagrammatic side view of the brain of Hatteria punctata. 

 The brain is lying in its cartilaginous case. From the thalamencephalon 

 between the cerebral hemispheres and the optic lobes arises the epiphysis, 

 which at first running almost directly upward, turns forwards on reaching the 

 cartilaginous roof as far as the parietal foramen, where the pineal stalk pierces 

 the cartilage and enters the optic vesicle, which is seen lying in its capsule. 



Fig. 9. — External view of the modified eye-scale of Cyclodus, showing 

 the modification to form a cornea. 



Fig. 10. — External view of the scales in the median line of the head of 

 Varanus giganteus, showing the scale modified as a cornea. 



Fig. 11. — The pineal eye of Anolis (sp. ?) removed, together with the 

 brain membranes, and viewed as a solid object by transmitted light. 



Fig. 12. — The pineal eye of a small specimen of Varanus bengalensis, 

 ying within the parietal foramen and viewed from the under surface. 



Fig, 13. — The modified eye-scale of a small Calotes (sp. ?), with the trans- 

 parent cornea in the middle through which the eye is seen. 



Fig. 14. — The pineal eye of the same Calotes, whose scale is figured in 

 Fig. 13, removed with the dura mater and viewed as a solid object. 



Fig. 15. — Scales from median line on head of a large specimen of Iguana 

 tubereulata, showing the modified eye-scale with cornea. 



Fig. 16. — Modified eye-scale of a young Iguana, showing the transparent 

 central portion with the eye beneath as a dark spot. 



PLATE XVI. 



Fig. 17. — Longitudinal vertical section through the parietal foramen of 

 Varanus bengalensis, showing the pineal eye and the hollow epiphysial 

 stalk immediately beneath. The yellow shade indicates bone. Ep} Hollow 

 epiphysial stalk. 



Fig. 18. — Jjongitudinal vertical section through the distal part of the 

 epiphysis of Cyclodus, showing the swollen extremity and the hollow epi- 

 physial stalk connecting this with the brain. Ep. 1. Swollen extremity. 

 Ep} Epiphysial stalk. 



