268 VERTEBRATE ZOOLOGY 



The Lateral Aspect. The temporal bone is here seen in its entire 

 extent. It is made up of three principal portions: a dorsal, ex- 

 panded squamous portion, which bears the zygomatic process ; a 

 tympanic portion, which forms the tympanic bulla and contains 

 the external auditory meatus; and a petrous portion, which is 

 the hinder and inner part and contains the inner ear. Just back 

 of the external auditory meatus is the stylomastoid foramen, for 

 the passage of the facial nerve, beneath which is a deep pit re- 

 sembling a foramen. The prominent mastoid process projects 

 ventrally at this point, lying against the side of the bulla. Just 

 in front of this foramen are four foramina in a row, the one near- 

 est it being the foramen ovale, for the passage of the mandibular 

 branch of the trigeminal nerve ; the next one, the foramen rotun- 

 dum, for the passage of the maxillary branch of the trigeminal ; 

 the next, the orbital fissure, for the passage of the oculomotor, 

 trochlear, and abducens nerves, and the ophthalmic branch of the 

 trigeminal ; and the anterior one, the optic foramen, for the passage 

 of the optic nerve. 



In the anterior margin of the orbit are two foramina, the dorsal 

 and smaller one being the lachrymal foramen, through which the 

 nasolachrymal duct passes to the nose ; the ventral one being the 

 infra-orbital foramen, through which an artery and a branch of 

 the maxillary nerve pass from the orbit to the face. A short 

 distance back of these are two foramina close together,— the 

 sphenopalatine foramen, the larger one, and the palatine foramen, 

 through which small arteries and nerves pass. 



Exercise 58. Draw a view of the lateral aspect ; carefully outline the 

 bones of the orbit, as well as the others which appear. 



The Ventral Aspect. In front of the occipital is the basisphe- 

 noid bone, and in front of that the small presphenoid. The paired, 

 lateral projections of the former are homologous to the alisphe- 

 noids of lower vertebrates ; a pair of processes projecting ventrally 

 in front of these are the pterygoid processes, which are homol- 

 ogous to the parasphenoid bone of lower vertebrates. The paired 

 lateral projections of the presphenoid are homologous to the orbito- 

 sphenoid bones of the lower vertebrates ; the large optic foramen 



