266 Proceedings of the Royal Physical Society. 
crowns much worn down and hollowed out in the middle, 
showing the central brown dentine, surrounded with a 
coat of enamel, and a slight outer layer of dark coloured 
cementum. 
There are fifteen molar teeth remaining in the upper jaw, 
and fifteen in the lower, with six distinct empty sockets ; 
the dental formula in the skull from Honduras is, therefore, 
9 — 9 
m g-^Tg = 36. It appears to have been from the American 
species, the 3Iandtus australis of the British Museum Cata- 
logue, that Daubenton, Cuvier, Gray, and others, have 
adopted the dental formula of the genus Manatus. In the 
British Museum Catalogue for 1850, the number of grinders 
in the genus Manatus is said to vary according to the age or 
9 — 9 
state of the specimens, but when complete to be m ^ — ^ = 36. 
It is added that the front ones are often deciduous ; hence 
6—6 
Sir Everard Home describes them as m g — ^ = 24, and 
Cuvier as m g^^^g = 32. 
There is no skull of the African species mentioned in the 
Catalogue as existing in the British Museum ; and there is 
none described in the Catalogue of the Eoyal College of Sur- 
geons of London ; and at a meeting of the British Associa- 
tion held at Cheltenham in 1856, Professor Owen stated, 
that he had not then had an opportunity of examining the 
dentition of the known African Manatee. 
The difference in the number of the molar teeth in these 
two distinct species corresponds with the difference in the 
length of the aveolar portion of the palate, and with other 
corresponding modifications which have been shown to 
exist between the two skulls. 
I am indebted to Professor H. D. Bogers of Glasgow for 
an opportunity of comparing the skull of the Manatus aus- 
tralis, with that of the Manatus senegalensis ; and the result 
of this anatomical comparison appears to me to justify the 
conclusion, that m — = 44^ is the normal number of 
the dental formula for the genus Manatus, as this number 
