Fig. 7. Multifocal optical systems and slit pupils in large-eyed terrestrial vertebrates. Clearly visible ring-like structures were observed in photorefractive images of the eyes of domestic sheeps (Ovis aries domesticus; A) which have horizontal slit pupils (B). Similar pupil shapes were found in other artiodactyls, such as the reindeer (Rangifer tarandus; C). The Nile crocodile (Crocodylus niloticus; D) has a vertical slit pupil in combination with a multifocal optical system. Scale bars are 10 mm.