274 



MAMMALIAN ANATOMY 



of the foramen rotundum ; below this foramen and continued on the 

 front of the pterygoid process is a spheno-maxillary surface which 

 forms the posterior part of the spheno-maxillary fossa, In the medial 

 superior corner is the anterior opening of the Vidian canal. The 

 lateral surface of the great wing is divided by a horizontal infratem- 

 poral crest into an upper temporal surface and a lower zygomatic 

 surface. The scaphoid fossa is limited to an oval depressed area on 

 the upper part of the posterior edge of the inner pterygoid plate. The 

 hamular process is a curved rod, which is very variable in size and 

 shape. The foramen ovale is relatively much larger than the cor- 

 responding opening in the sphenoid of the cat ; lateral to it is a smaller 

 opening, the foramen spinosum, for the meningeal vessels, which is 

 not present in the cat. 



FIG. 197. 



8 



19 



25-' 



20 



THE SPHENOID BONE. POSTERIOR ASPECT. 



1, dorsum selte; 2, anterior clinoid process; 3, posterior clinoid process; 4, small wing; 5, sphenoidal 

 fissure ; 6, great wing, intracranial surface ; 7, parietal angle ; 8, squamous border ; 9, carotid groove ; 10, posterior 

 surface of body ; 11, spheno-petrosal lamina; 12, infratemporal crest; 13, Vidian canal; 14, basipharyngeal canal ; 

 15, zygomatic surface of great wing; 16, pharyngeal canal; 17, scaphoid fossa; 18, pterygoid fossa; 19, external 

 pterygoid plate ; 20, internal pterygoid plate ; 21, sphenoidal crest ; 22, sphenoidal rostrum ; 23, vaginal process ; 

 24, hamular process ; 25, groove for tensor palati muscle ; 26, pterygoid fissure closed by palatine bone ; 27, pterygoid 

 process. 



The region of the great wing behind the foramen ovale is reduced 

 to a narrow strip which is bent sharply dorsally and backward from 

 the inferior surface and is known as the spheno-petrosal lamina. In 

 this way the posterior end of the vaginal process (the vaginal tubercle) 

 and the posterior opening of the Vidian canal are brought close to 

 the apparent posterior margin of the bone. Medial to the spheno- 

 petrosal lamina is the lingula, much reduced in size, but supporting a 

 more clearly defined carotid groove. A short groove leading ventrally 



