406 DR KNOX on the Dentition of the Dugong, and on the 



raarkable. There are alveolar cavities for six teeth in the upper 

 jaw on each side, and a similar appearance in the lower jaw ; 

 these teeth may once have been conical, but, by use, they are 

 much flattened above, and sloped. These anatomical differences, 

 found to exist in animals so greatly resembling each other, are 

 remarkable. 



Of the Size of the Foetus of the Cetacea at the time of Birth. 



Naturalists, I presume, must have few well authenticated 

 facts on this point, otherwise it would not happen that so able a 

 naturalist as the author of the British Zoology should have de- 

 scribed the fcetus of the Delphinus Phocana as being only seven 

 inches in length shortly before birth *. I have put on the table 

 of the Society the skin of the fcetus of a common porpoise, of the 

 usual length (about five feet two inches), and which was caught 

 in the Frith of Forth. It was removed from the uterus, toge- 

 ther with its membranes, in presence of a numerous class. The 

 length, even in its present dried state, is two feet six inches, and 

 I see no reason, from the state of the parts, to suppose that the 

 birth of the young was about to happen at the moment of the 

 capture of the mother. The foetus of the seal is, in like manner, 

 of a disproportionate size to its parent f. Its birth is provided 

 for by a remarkable mechanism connected with the fibro-cartila- 

 ginous and ligamentous structure of the symphysis of the pubis, 

 which, previous to, and during parturition, elongates to the ex- 

 tent of nearly two inches. The effects of this, in enlarging 



* British Animals. 



f The foetus of a seal shortly before birth was found to be about 2 feet 6 inches 

 in length, that of the mother being about 5 feet 2 inches. 



