Figs. 475 to 480.— The Visual Cells of Snakes (x 1,000) (Gordon Walls). 



Fig. 47.5.— The 3 cone-types (A, B, C) 

 constituting the fundamental pattern in 

 diurnal forms (drawn from the European 

 grass snake, Tropidonotus natrix). 



Fig. 477. — Visual cell types of scotopic 

 colubrids. 



Fig. 479. — \isuai cell types of the African 

 puff-adder, Bitis arietans (strongly 

 nocturnal in habit). The Type C (rod) 

 is the most abundant element. 



Fig. 476. — The 3 rod-types in the spotted 

 night snake, Hypsiglena. 



P'iG. 478. — Visual cell types of the crota- 

 lids. Type C is a rod containing 

 rhodopsin. 



Fig. 480. — Visual cell types of the Cape 

 viper, Causus rhomheatus (crepuscular 

 in habit). There are two variations of 

 TyjDe C, Type C (rod) being most 

 abundant. 



