THE PINEAL SYSTEM OF AGAMIDA 275 



Agama caucasica (Owsjannikow, 1888). 



The parietal eye, which was exceptionally large, lay in a parietal 

 foramen surrounded by connective tissue containing numerous pigment 

 cells. Both lens and retina showed cells the inner ends of which terminated 

 in pencil-like refractile processes which projected into a vestigial vitreous 

 body. 



Grammatophora (Spencer, 1886 ; McKay, 1888). 



In Spencer's specimen the parietal eye was spherical and strongly 

 pigmented in its lower segment. Externally it was covered by a white 

 substance. Superficial to it the tissues contained no pigment and there 

 was a conspicuous corneal scale. McKay's case has already been alluded 

 to (p. 273). 



Moloch horridus (Spencer, 1886). 



The parietal spot was visible in the middle of a small area surrounded 

 by horny processes, which cover the skin in this region ; it appeared 

 as a black dot surrounded by a dark circular rim. The parietal organ lay 

 in a parietal foramen and was continuous, by means of a slender cylindrical 

 stalk, with the epiphysis. This widened out insensibly into a conical 

 epiphysis. The stalk was solid throughout. The interior of the parietal 

 organ was almost completely filled with pigmented tissue, and the lens 

 was absent. 



Jguanidae. 



This family, which closely resembles the preceding, comprises very 

 various species, which are mostly found in America and in neighbouring 

 islands such as the Galapagos. Some, such as Anolis, are arboreal ; 

 others, such as the snub-nosed Amblyrhynchus cristatus, live to a great 

 extent in the sea and feed on seaweed. The Californian toad Phrynosoma, 

 which is found in the United States of America and in Mexico, lives in 

 sandy deserts and preys on small beetles and other insects. The girdled 

 lizards Zonuridae are remarkable for the primitive character of their 

 skulls, the hinder and lateral parts of which are completely roofed over by 

 dermal bones. 



In contrast to the Geckonidse, the parietal organ is usually present and 

 well developed, and the Iguanidse in this respect resemble the Agamidse 

 and the remaining families of Lacertilia which we shall describe in the 

 following pages. The parietal organ is usually well developed and lies 

 beneath a transparent scale, near the centre of which is a circular dark 

 spot surrounded by a pale rim. The epiphysis is usually subdivided 

 into a proximal thick-walled part, a stalk, a flattened vesicle, and frequently 

 a fibrous cord which connects the tip of the epiphysis with the parietal 



