Auditorj/ Apertures as Auxiliaries iii Classification. 9 



Art. III. On the Auditory Apertures in the Shulls of Qttadrupeds 

 and Birds, as auxiliaries in Classification, By W. Farrar, 

 Esq., M.D. 



Sir, 

 I HAVE been induced, for some time back, to pay a con- 

 siderable share of attention to the position of the auditory 

 canal in various animals, from having accidentally remarked, 

 when engaged in researches m comparative anatomy, the dif- 

 ferent situations of this tube in the pursued and pursuing ani- 

 mals. From what has fallen under my notice, I think this 

 portion of the animal structure has received but little atten- 

 tion ; at any rate, much less than I feel inclined to claim for 

 it. I am further of opinion, that the form and situation of 

 this organ, or its tubulated external portion, might be made 

 a very useful auxiliary in classing quadrupeds (and particu- 

 larly the fossil specimens of them), as well as in arriving at a 

 more correct knowledge of their habits and modes of exist- 

 ence. I have selected a few well known animals, to show the 

 most opposite extremes in which the auditory canal is placed, 

 for the amusement, if not for the edification, of your readers. 

 To commence with the skull of the hare. ( fig. 3.) When 



the skull of 

 3 .„ai^^^^^^^^^ the animal is 



placed hori- 

 zontally before 

 you, the tu- 

 bulated bony 

 portion of the 

 external ear 

 is seen nearly 

 half an inch in 

 length, and a 

 quarter of an 

 inch in diame- 

 ter, pointing backwards and upwards, at an angle of 45° or 

 thereabouts. To this tube (a) in the living animal is attached 

 the external ear, which is moved in various directions to suit 

 the purposes of the animal, as will be subsequently mentioned. 

 This animal is a pursued one ; and, as such, it is indebted for 

 its safety to a quick perception of danger, by means of its ex- 

 ternal senses. The least remarkable of these is certainly not 

 that of hearing : viewed externally, we find long open ears, for 

 the most part inclining backwards ; but also occasionally for- 

 ward, as well as laterally. These are moved into various 

 attitudes by muscles placed for that purpose, and thus serve 



