and organs of hearing of the dugong. 151 
principal part of their food. It is from him we learn that their 
usual length is twenty feet ; but that catching them full grown 
was a service of danger ; nor were they so delicate as food for 
the table. This gentleman’s account was published in 1720, 
and is written with so much apparent candour, that there is 
no reason for doubting the veracity of his narrative. 
As these habits are allied to those of the hippopotamus, I 
inquired whether this peculiarity of structure exists in the ear 
of that animal, but find there is nothing of the kind ; all the ossi- 
cula are separate, and very readily drop out of the cavity of the 
tympanum when the skull is deprived of the soft parts. There 
are peculiarities in the mechanism of this organ in the hippo- 
potamus which deserve being mentioned. The projecting 
ear and meatus auditorius externus, have a higher situation 
upon the head than in most other animals ; and the tube that 
passes down to the membrana tympani, is one straight line. 
The bony portion of it is four inches long, its direction from 
the external surface of the head down to the membrane, 
is at an angle of 4,5°, and its termination is upon a ledge which 
forms a slight projection beyond the bony ring to which the 
membrana tympani is attached ; the space on the outer sur- 
face of the membrane, between it and the opposite side of 
the tube, is so small, that it cannot exceed the thickness of 
the membrane itself. The ossicula are small, when the size 
of the animal is considered ; but the cochlea makes two turns 
and a half, which is by no means common ; the semicircular 
canals have the usual appearance. 
This animal I understand, from every enquiry I have been 
able to make, when it goes down into the water to feed at the 
