394 



THE SENSORIAL FUNCTIONS. 



brane, which must here be regarded as an ear-drum, 

 to the membrane of the vestibule, or fenestra 

 ovalis, is found a bone, shaped hke a trumpet, and 

 termed the Coliunella. This bone is seen at c in 

 Fig. 404, attached by its base (b) to the fenestra 

 ovalis of the vestibule (v), which contains the cre- 



taceous body (o). There is also a small bone (i) 

 attached in front to the columella. In the Chelonia, 

 the structure of the ear is essentially the same as 

 in the Frog, but the tympanum and columella are 

 of greater length. In the saurian reptiles the cavity 

 of the tympanum is still more capacious, and the 

 ear-drum very distinctly marked ; and these ani- 

 mals possess great delicacy of hearing. The laby- 

 rinth of the Crocodile is enclosed in bone, and 

 contains three calcareous bodies : it presents also 

 an appendage which has been regarded as the 

 earliest rudiment of a cochlea ; and there are two 

 folds of the skin, resembling eye-lids, at the ex- 

 ternal orifice of the organ, which appear like the 

 first step towards the developement of an external 

 ear. 



The structure of the ear in the Crocodile is but 

 an approximation to that which we find prevailing 

 in Birds, where the organ is of large size compared 

 with that of the head. The rudimental cochlea, as 

 seen at k in Fig. 405, which represents these organs 



