368 HALICORE. 



constriction: the first molar was lost in both jaws, and the second 

 was shed on the right of the upper jaw. A male Dugong, with a 

 skull fourteen inches and half in length, with the sockets of the 

 deciduous tusks obliterated, and the permanent tusks protruded to 

 the usual extent and worn by use, had the molar teeth reduced 

 to two on each side of both jaws, the grinding surface of the last 

 presenting the hour-glass shape, analogous to that of the worn 

 posterior grinders in the Zeuglodon ; but the fang of this tooth does 

 not become divided in the Dugong. 



The period when the molar series can be viewed in its most 

 complete state in the Dugong is that represented in PI. 92. These 

 teeth increase very regularly in size : the fang of the first c, and 

 of the second d, is soon completed and solidified ; that of the third 

 e is more elongated and retains its basal cavity longer ; but it 

 becomes at length contracted to a point, solidified, partially absorbed, 

 and the tooth is then shed : the crown presents an irregular oval 

 shape in transverse section. The fourth molar tooth, when fully 

 formed, resembles a slightly bent cylinder with a nearly smooth 

 outer surface ; the crown is flat, or slightly depressed at the centre. 

 The opposite extremity of the tooth is excavated by a regular conical 

 cavity, lodging the remains of the pulp (PI. 93, fig. 5). With age, 

 however, the fang contracts, takes on an irregularly fluted and tuber- 

 culate surface, and is at last closed at its extremity. The matrix 

 of the last molar tooth expands as the crown is forming and mani- 

 fests a tendency to divide into two fangs ; but, having acquired the 

 size and form exhibited in fig. 6, PL 93, the pulp is maintained in 

 a wide basal pulp-cavity to supply the waste of the crown according 

 to that pattern. 



The molar teeth of the Dugong consist of a large body of 

 dentine, a small central part of osseo-dentine, and a thick external 

 investment of cement. The disposition of the calcigerous tubes, as 

 displayed in a transverse section near the base of the crown of the 

 first molar, is shown in the reduced figure of a highly magnified view 

 in PI. 94. They have a sinuous course for a certain extent from 

 the pulp-cavity, in which they frequently bend in opposite instead 

 of parallel curves, and here and there form loops, convex towards 



