THE SKULLS OF REPT1LTA AND AYES. 



233 



tube can hardly be said to exist. In the Ophidia and in certain 

 Laeertilia the tympanic cavities and Eustachian tubes are alto- 

 gether absent, and, even in the higher Laeertilia, the tympanum 



can hardly be said to have definite bony walls. In the Chelonia, 



Fig. 95. 



B 



C 



7 J mx 



JPm/x 



die 



Fig. 95. — Views of one half of the palatine surface of the skull in (A) an Ostrich, (B) a 

 Crocodile, (C) a Python. N, the posterior nasal aperture (median nares of Man) in 

 the Bird. The dotted line traverses the posterior nasal aperture, situated between 

 the palatine, the vomer, and the maxillary. The corresponding opening is placed be- 

 tween Vo and PI in the Snake. N 1 , the posterior nasal aperture, or posterior nares, 

 of the Crocodile. 



on the other hand, the opisthotic and the pro-otic bones are 

 produced outwards so as to form the anterior and posterior 

 boundaries of a cavity, the antivestibulam Bojani — -which is 

 bounded externally by the great quadrate bone. The latter is 

 funnel-shaped, and deeply notched posteriorly and inferiorly. 

 The tympanic membrane is fixed to the margins of the funnel, 

 and the so-called " columella" which answers to the stapes, is 

 fastened by one end to this tympanic membrane, and tra- 

 versing the notch and entering the antivestibulum, passes to its 

 other insertion into the membrane of the fenestra ovalis. The 



