144 ME. A. H. GAEEOD ON THE MANATEE. 



since the publication of Dr. Murie's statement as to these cervical nerves, careful search 

 was made with the view of confirming his statement, and the condition described by 

 him was not found to obtain ; but the usual and normal arrangement of a single pair of 

 cervical nerves between each successive pair of cervical vertebrae 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 structure, 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 examina- 

 tion 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 cross- 

 ing of the contiguous layers (decussation 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 appear- 

 ance 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 crovpn 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 regularity. 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 lacunae are richly sup- 

 plied with canaliculi. 



" It 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 resem- 

 blances to the Tapir's tooth, which, though they may be purely accidental, are remark- 



