28 



TRANSACTIONS OF WAGNER 

 MASTODON 



Estimated diameter fore and aft of the crown 

 Transverse diameter at base of first pair of lobes 

 Transverse diameter at base of second pair of fobes 

 Transverse diameter at base of third pair of lobes 

 Transverse diameter at base of fourth pair of lobes 

 Height of first outer lobe .... 



Height of third outer lobe . . . 



Height of fourth outer lobe .... 



Height of fifth outer lobe ..... 



190 mm. 



73 

 72 

 66 

 66 

 70 

 67 

 57 



Among the characteristic specimens of the Mastodon from Mixon'splan- 

 tation are three, two of which, the isolated crown of a right upper molar 

 tooth and a fragment of the left maxilla, with another molar, were received 

 in . the earlier collection, while the third specimen, a larger fragment of the 

 opposite maxilla, with the corresponding tooth to that of the former one, was 

 received in the collection of 1890. The three specimens appear to have 

 belonged to the same animal, an individual of medium age and comparatively 

 of small size. The isolated molar I at first viewed as a first true molar, but 

 its correlation with the specimen last observed leads me to regard it as the 

 second of the series, and those in the jaw fragments as the first in the same 

 series. 



Plate ii. fig. 6 represents the crown of the upper second true molar. It 

 is complete, and is only a little worn on the summit and anterior extension of 

 the first internal lobe. It may be regarded as typical of the intermediate 

 molars of the series in the species. 



The crown is composed of three pairs of lobes, embraced by a basal 

 ridge and separated by transverse valleys, which are divided along the middle 

 of the tooth by strong tubercular offsets of the inner lobes. In each trans- 

 verse pair of lobes they are separated by an angular notch, which becomes 

 successively deeper from the first to the last. The inner lobes are the larger, 

 and are conical, with the lateral surface continuous fore and aft and promi- 

 nently convex, and medially expanding in front and behind in strong buttress- 

 like ridges. These extend from the summit, are divided into tubercular 

 eminences, and in the valleys conjoin so as to obstruct their course, but leave 

 angular notches between the summits of the lobes. A tubercular offset, 

 variably produced from the medial surface of the inner lobe, is directed to the 

 contiguous outer lobe. It is best marked in the first inner lobe and least in 

 the last one. In the last inner lobe also the posterior buttress-like ridge is but 



