708 



REPTILIA. 



a circumstance evidently intended to prevent air or fluid from being 

 pent up in the tympanic chamber and thus interfering with the free 

 vibration of the drum. 



(2000.) In Serpents, Fig. 349. 



on account of the pecu- 

 liar disposition of the 

 pieces of the temporal 

 bone, before described 

 ( 1907), there is no 

 tympanic cavity, and the 

 columnella (fig. 335, v) 

 is absolutely imbedded 

 in the flesh; the arrange- 

 ment, however, in other 

 respects is the same as 

 in the generality of rep- 

 tiles. 



(2001.) The lower 



tribes Of Amphibia, as Ear of the Tortoise. 



we might be led to ex- 

 pect from their close approximation to Eishes, have neither tympanum 

 nor columnella, and thus, like Fishes, can only hear in an aquatic 

 medium. 



(2002.) The membranous labyrinth of Beptiles (fig. 350, a, 6, c) cor- 

 responds in its general conformation with that of Fishes, presenting the 

 same semicircular canals, ampullae, and vestibular cavity, and more- 

 Fig. 350. 



Auditory and olfactory apparatus of the Turtle. 



over the sacculus contains cretaceous concretions or otoliths of a similar 

 character ; but in this class the membranous canals become enclosed 

 in a bony sheath, moulded as it were upon their outer surface, 



