436 



TEXTBOOK OF ZOOLOGY 



The sense organs include the eyes, the olfactory organ, internal ear, 

 and the lateral line system. The eyes are in the orbits, one on each 

 side of the cranium. They are quite typical of the vertebrate eye 

 described in the general chapter on phylum Chordata. The olfactory 



OUPACTORV 

 e>ULB 



OUFACTORV 

 TRACT 



CEREBRUM 



MAX>LUAR.*S 



OPTIC LO&E 



OPHTHALMICUS 

 SUPERFICIALIS 



OPHTHALMICUS 

 PROFUNDUS 



MANDI&ULARIS 



TRIGEMINAL 



FACIAL 

 PALATINUS 



AUDITORY 



HYOMANDIBULARIS 



OLOSSOPHARYNGEAL 



VAOUS 



TERMINAL 



OPTIC 

 TROCHLEAR 



OCULOMOTOR 

 A60UCENS 



CORPU& 

 RESTIFORMUS 



MEDULLA 



Fig. 235. — Dorsal view of the brain and cranial nerves of the dogfish shark, 

 Sgualus acanthias. (From Atwood : Introduction to Vertebrate Zoology, published 

 by The C. V. Mosby Company.) 



organ consists of a pair of nasal sacs on the ventral side of the ros- 

 trum which open by nostrils. The nasal chambers are blind sacs and 

 lined with a sensory lamellated olfactory membrane in which the 

 olfactory nerve ends. The internal ears are composed of a vestibule 



