346 



of the bands, the thickness of the plates of enamel, the smoothness of their 

 sides, and the great depth to which the notches forming the digitated 

 processes extend. So strong, indeed, are all these characters, and so 

 nearly do the upper terminations of these plates approximate to the pro- 

 tuberances on the grinders of other animals, and particularly of the mam- 

 moth, as to give room for the conjecture, that this tooth may have be- 

 longed to an animal, possessing intermediate characters between those 

 of the elephant and those of the mammoth. 



The specimen, the surface of which is represented Plate XX. Fig. 5, 

 also varies considerably from the recent as well as from the common fos- 

 sil teeth, in the form and arrangement of its plates. This tooth, an up- 

 per tooth of the left side, which I purchased at the sale of Rackstrow's 

 Museum, was described in the catalogue as having been taken up with 

 ballast from the bottom of the Thames. 



Of the variation which takes place in the form and arrangement of the 

 plates in this tooth, it is very difficult to give a description. In the recent 

 teeth, and in the common fossil teeth, the plates are continued straight 

 across the tooth, the enamel being disposed in a long elliptical line, in 

 which the osseous part, or the ivory of Mr. Home is included. Hence, 

 by the abstraction of the surrounding crusta petrosa, as we have already 

 seen, frequently is the case with the fossil teeth, the tooth falls to pieces, 

 and each flat plate is found separated. 'But in the specimen, which has 

 been just examined, an irregularity may be observed in the third ante- 

 rior row of the plates, where the two digitated processes of a plate passing 

 over little more than half the width of the tooth are interposed between 

 the second and fourth plate, and thrust a portion of the latter plate ra- 

 ther aside. It is an extension of this peculiarity of form which, in part, 

 characterizes the present tooth, since very few of the plates, of which it 

 is formed, pass directly across : leaving it difficult to say, how the osseous 

 part is disposed. 



But the most characteristic peculiarity of this tooth is, the continuity 

 of many of its plates, and the remarkable DaBdalian line in which the 



