PUPIL OF THE EYE 93 



latter has a beaded appearance, the beading 

 corresponding with the previously noted crenula- 

 tions. Crocodiles also show the narrow vertical 

 pupil. 



Among snakes, round and vertical pupils occur 

 with nearly equal frequency, the former rather 

 more frequently than the latter ; but Dryophis, 

 called the whip-snake, has a very pronounced 

 horizontal pupil (Fig. 6). 



Fig. 6. 



Head of Dryirphis pulvervlentus in side view. 



In the class Mammalia the round pupil pre- 

 vails, whereas the vertical pupil, as mentioned 

 above, characterises certain groups. The oblong 

 horizontal pupil of the horse, camel, ox, and sheep 

 was referred to by Owen in his "Anatomy of 

 Vertebrates" (1866); it is very sharply defined 

 in goats that have a gilt-edged iris. Owen also 

 stated that in a dead Agouti (Rodentia) the 

 pupil was a horizontal ellipse ; but he did not 

 allude to the horizontal pupil of the mungoose, 

 nor have I seen it mentioned in any other work 

 so far as I can remember. In the Civet family 

 (Viverridae), which is closely allied to the Felidae, 

 the vertical pupil appears to be the rule, but 



