58 



REMARKS ON THE DENTAL SYSTEM OF THE MASTODON. 



three. The first is a large adult with two of the largest class of molars on each 

 side: it is perfect, with the exception of a small fractured surface of the left ante- 

 rior part of the chin. This specimen has a lower maxillary tusk, twenty lines in 

 diameter and five inches long. It protrudes from the anterior right side of the 

 chin, and is directed horizontally. There is not the smallest indication of there 

 ever having been a similar production from the left side of the chin, the frac- 

 ture of which has not been deep enough to remove such vestiges, had they 

 existed. The second specimen is also an adult lower jaw of the same size, in 

 which the whole of the chin and the left half of the bone remain. In the 

 right side of the chin, there is a horizontal alveolus, the size of the preceding; 

 the tusk is not in it, but there is a loose one in the cabinet which may have 

 belonged to it. In this jaw there is no corresponding alveolus, or even a ves- 

 tige on the left side. The third specimen is the chin alone, of a very young 

 and small animal, it is three inches in length by one and a half wide, is fossil- 

 ized, and cemented thereby to a fragment of limestone about its own size. Here 

 an alveolus for an inferior maxillary tusk exists also for the right side, but not 

 on the left. 



The dentition of these three specimens is, by a very curious coincidence, not 

 symmetrical, that is, a tusk exists only on the right side of the chin in each. 

 The questions in regard to the Tetracaulodon of Godman, are rendered still 

 more embarrassing by their existence; for are we to consider them merely as 

 abnormal types of that animal — as known Mastodons — or as still another species, 

 to which, if such, the name of Tricaulodon might be attached? I confess my^ 

 self unable to suggest a probable solution of this difficulty. Connected with it 

 is, in fact, another: Mr. Koch has the lower part of the head of a Mastodon of 

 middling size in which, from the intermaxillary bone, as usual, protrudes a tusk; 

 but the tusk exists only on the left side, there being not even a vestige of alve- 

 olus on the right. We are informed by Tavernier, that some examples of the 

 Elephas Indicus have but one tusk; are we, then, to consider this head as an 

 abnormal instance of the common Mastodon, or is there really an extinct animal, 

 which has an inferior maxillary tusk on the right side, and a superior maxil- 

 lary on the left? Each jaw sacrificing one tusk. 



The minute anatomy of the teeth, as exhibited by the microscope, has lat- 

 terly been a very favourite object of study. The unquestionable result appears 

 to be, that there are well established differences of texture in different animals, 



