138 FREDERICK TILNEY AND LUTHER F. WARREN 



pears. The pigment increases in the older animals. The lens 

 is plano-concave. The eye rests in a parietal foramen. The 

 cornea is present as well as a marked parietal spot. 



7. Phrynosoma douglassi. Ritter ('91). 332 There is an epi- 

 physeal vesicle in this form and a posteriorly flattened vesicle 

 which contains no lumen. It is connected by a very thin stalk 

 to the epiphysis. The parietal eye is connected with the brain 

 roof and is a laterally compressed vesicle. The lens and retina 

 are both well developed. The retina has an outer cell layer, a 

 molecular layer, and an inner layer with two elements, one round 

 and the other elongated, and finally an inner layer of rod cells. 

 There is a coagulum in the cavity of the eye vesicle. The lens 

 is slightly bi-convex. The nuclei of the lens cells lie near the 

 inner periphery of the lens. The position of the eye is in a 

 broad foramen. The parietal cornea and pit, as well as a pari- 

 ietal spot, are all present. 



8. Uta stansburiana. Ritter ('91) ; 332 Studnicka ('95). 386 The 

 parietal eye in this form is also ventrally flattened. The lens is 

 separated from the retina. There is deep pigment in the retina 

 and the eye rests in a parietal foramen. 



9. Sceleporus undulatus. Herrick ('9 1) 178 in describing the 

 epiphysis in this form, states that the .under wall has some 

 similarity to the retina. 



10. Phrynosoma coronatum. Ritter ('91) ; 332 Sorensen ('93). 361 

 The epiphysis is similar to that in Phrynosoma douglassi. It is a 

 thick-walled vesicle. The cells in the interior are deeply pig- 

 mented. There is a connective-tissue strand running to the 

 parietal eye. The parietal nerve extends from the commissura 

 posterior to the parietal eye. The eye is not as well differ- 

 entiated as in Phrynosoma douglassi, although it is present. 



11. Sceleporus striatus. Sorensen ('94). 363 In this form the 

 epiphysis is attached to the roof by a thin, peculiarly white 

 stalk. The parietal nerve presents no peculiarities, but arises 

 from the anterior portion of the commissura habenularis. It is 

 solid to the extreme end of the epiphysis where it proceeds to 

 the parietal eye, the latter apparently being independent of the 

 end of the epiphysis. No parietal foramen is present. The 



