THE TEETH OF GET AGE A. 309 



obliteration of the pulps by calcification, 1 so that the pulps 

 died and abscesses around the teeth had resulted. 



In the sperm whale the teeth are numerous in the lower 

 jaw, but in the upper jaw there are only a few curved, 

 stunted teeth, which remain buried in the dense gum. The 

 teeth of the lower jaw are retained in shallow and wide de- 

 pressions of the bone by a dense ligamentous gum, which, 

 when stripped away, carries the teeth with it. Every inter- 

 mediate stage between this slight implantation and the 

 well-developed stout sockets of the grampus, is met with in 

 the Cetacea. 



In the bottle-nosed whale (Hyperoodon bidens) the only 

 large teeth present are two conical, enamel-tipped teeth 

 (sometimes four) which remain more or less completely 

 embedded within the gum, near to the front of the lower 

 jaw: in addition to these there are 12 or 13 very small 

 rudimentary teeth loose in the gums of both jaws. (Esch- 

 richt, Lacepede.) 



In the narwal (Monodon monoceros) two teeth alone per- 

 sist, and these are in the upper jaw. In the female the 

 dental germs become calcified, and attain to a length of 

 about eight inches, but they remain enclosed within the 

 substance of the bone, and their pulp cavities speedily fill 

 up. In the male, one tusk (in some very rare instances 

 both) continues to grow from a persistent pulp till it at- 

 tains to a length of ten or twelve feet, and a diameter of 

 three or four inches at its base. This tusk (the left) is 

 quite straight, but is marked by spiral grooves, winding 

 from right to left. It is curious that in one of the speci- 

 mens, in which the two tusks had attained to equal and 

 considerable length, the spirals on the two wound in the 

 same direction ; that is to say, as regards the sides of the 

 head, the spirals were not symmetrical with one another. 



( l ) Trans. Odonto. Society, 1873. When I published this paper I was 

 not aware that Eschricht had previously published a similar observation. 



