ON THE MANATEE. 311 
pair of cervical nerves between each successive = of cervical verte- 
‘bree was in both cases ascertained with precision.’ 
Mr. C. S. Tomes has also kindly examined the minute structure of 
the teeth, with the following results :— 
“ The teeth of the Manatee present several peculiarities of struc- 
ture, and the resemblance in external form which they bear to those 
of the Tapir is not fully carried out in their histological characters. 
I am not acquainted with any one tooth which combines the characters 
of the tooth of the Manatee; and I believe that an examination of a 
microscopical section would serve, with certainty, to identify a tooth 
as belonging to this creature. 
‘** The enamel which thickly coats the crown is peculiar, in that its 
prisms pass from the dentine to its surface in perfectly straight lines, 
so that there is none of that crossing of the contiguous layers (decus- 
sation of the enamel prisms) nor of that waviness of course which are 
supposed to lead straight to the enamel of most of the animals. 
** The whole thickness of the dentine (in very thin sections) has 
an appearance as though made up of an immense number of globules 
aggregated together. This appearance is a common one in very soft, 
imperfectly formed human teeth, and is to be seen in the Dugong and 
in some Cetacea. 
“ The dentinal tubes of the crown of the tooth give off very many 
small branches, and each tube terminates in a very large elongated 
cavity, of irregular outline. It is common enough for dentinal tubes 
to terminate in the small irregular spaces which are found in the 
periphery of the dentine of the roots of teeth; but such a termination 
beneath the enamel in the crown of a tooth is very unusual. 
“* The dentine of the roots of the teeth is permeated by a series of 
channels far larger than the dentinal tubes, the so-called vascular 
canals. These leave the pulp-cavity at regular intervals, pursue a 
course towards the surface of the root similar to that of the dentinal 
tubes, and terminate by anastomosing with their neighbours, and so 
forming a network of loops beneath the cementum. 
** The dentinal tubes between the vascular canals are in no respect 
peculiar ; they are mostly cut before reaching the immediate surface 
of the dentine, which might be described as coarsely and roughly 
ossified, while its interior portions are developed with perfect regu- 
larity. The vascular canals exist in the dentine of the crown of the 
tooth. Of the cementum there is nothing to be said ; it is thick, and 
its lacune are richly supplied with canaliculi. 
**Tt does not appear to me that the histological characters of the 
tooth can be made much use of as indicative of its affinities; still it 
may be worth while to note resemblances to the Tapir’s tooth, which, 
though they may be purely accidental, are remarkable. My father, in Page 145. 
