136 Dr. J. E. Gray on the Species of Manatees. 



is rugged or produced into teeth between the notches on the 

 sides. But in one of the African skulls the front edge of the 

 frontal is truncated, thin, and torn, as in the American skulls; 

 but this has not any notch on the side for the reception of the 

 hinder ends of the nasals. 



The character of the form of the gonys of the lower jaw is 

 more variable and less distinctive. In four lower jaws from 

 Africa the gonys is convex, rounded, and but slightly grooved ; 

 and in three of the lower jaws of the skulls from America the 

 gonys is much more produced, compressed, and divided into 

 two rugosities by a central groove. Yet in one of the lower 

 jaws from Africa there is a slight indication of an approach to 

 the form of the tubercle in the American jaws; in one of the 

 American lower jaws the tubercle of the gonys is scarcely divided, 

 and less developed than in those above described, and in another 

 American lower jaw the tubercle is so like that of the African 

 specimen as not to be distinguished from it. 



The tubercle or tubercles in the front of the upper surface of the 

 incisive part of the lower jaw appear to be constant in the speci- 

 mens in the British Museum. They vary in size according to the 

 age of the specimen, being least developed in the younger ones. 



The flatness or concavity of this part of the lower jaw is not 

 so distinctive ; it is very concave in all African skulls, and flat in 

 the American ones; but the sides are more or less raised in the 

 different specimens. But, combined with the form of the tuber- 

 cle, it affords some assistance in determining the species. 



In all the African skulls the lower part of the aperture of the 

 nose is above a line drawn across the beak of the skull on a level 

 with the surface of the alveoli of the teeth. In all the American 

 skulls the aperture is similarly situated as regards such a line ; 

 but in one (the specimen from Jamaica), with a very largely 

 developed intermaxillary bone, the lower edge of the nasal aper- 

 ture is just on a level with such a line. 



After the most mature consideration and comparison of the 

 specimens from the different parts of Africa and America, and 

 the comparison of the figures on which the presumed species 

 from each of these countries have been founded, I have come to 

 the conclusion that, as far as the material at my command will 

 allow me to form an opinion, there is but a single species in 

 each locality. The species in each country vary in the size and 

 shape of the nasal cavity, in the length of the rostrum of the 

 skull, and the angle at which it is bent in regard to the line of 

 the palate, and also in the size and form of the intermaxillary 

 bones, and this even in specimens from the same locality, as is 

 proved by the observations of Dr. Kraus on the specimen from 

 Surinam. 





