MASTODON BORSONI. 



71 



In these fragments there are broad shallow channels. 



7th. Mastodon Borsoni. Second species of Swiss Molasse Mastodon. 



A superb, conglomerated, lignite specimen, containing three teeth in 

 situ, but dislocated, and judged to be of the upper jaw, right side. I 

 will describe the teeth from behind forwards, in the order of their com- 

 pleteness. 



These molars are at once distinguished, all of them, from the Mastodon 

 angustidens specimens, by the ridges being transverse, elevated, and 

 trenchant, without intermediate mammillae interrupting the valleys, and 

 by their general similitude to Mast. Ohioticus. 



The last tooth is in germ, and partly embedded on the inner side in 

 the alveolus, concealing the bourrelet. It is the penultimate or second 

 true molar, showing three transverse ridges intact. A mesial line of 

 longitudinal bipartition is seen. The points on the inner side are the 

 largest, and the inner division of the two front ridges consists chiefly 

 of this point. The posterior mesial surface of the front ridge sends 

 down a vertical keel as in the specimen of M. Borsoni at Turin. The 

 anterior talon is a transverse basal bourrelet, connected with the 

 front inner point by a vertical ridge. The bourrelet is continued 

 around the base on the inner side, but is partly concealed. The pos- 

 terior talon is an insignificant basal bourrelet, very little developed. 

 The three ridges are nearly of the same height and width, the crown 

 being oblong. 



Length of the tooth, 3-5 in. AVidth, at 1st ridge, 2-2 in. AVidth, 2nd ridge, 

 245 in. AVidth, 3rd ridge, 2-45 in. Height of crown (shell), l - 75 in. 



It agrees very nearly with the cast-measurement taken at Geneva, and 

 is evidently the same tooth. 



The next tooth in front is the 1st true molar (for reasons connected 

 with the next to be described). The posterior ridge and the inner half 

 of the middle ridge are broken off, giving no measurements. The 

 anterior ridge is entire and very slightly affected at the edge by wear, 

 trenchant as in M. Ohioticus, with a very pronounced basal bourrelet, 

 which is continued in front transversely in a basal slightly developed 

 talon. There is no interruption of the valley. 



Length of crown about 3-1 in. Width of 1st ridge, including bourrelet, 1-9 in. 

 Width of 2nd ridge, including bourrelet, 2-3 in. Width of 3rd ridge, about 2-4 in. 



The cast-specimen at Paris shows that this cannot be the third milk 

 molar. 



Immediately in front of the first true molar, but dislocated to the 

 inside of it, is an entire germ of a square tooth, with two transverse 



Mons. L. showed me several fragments of 

 a well-preserved tusk of compact tex- 

 ture and veiy hard, very different from 

 anything I saw with you at Seissan. 

 The section is round or oval, but has no 

 tendency to bo pyriform. The original 

 surfaeo is well preserved with a kind of 

 cortical outer layer, in some parts a good 

 deal sillune transversely with fine wavy 

 lines and no appearance of enamel (pro- 

 bal >ly the alveolar portion). It .was found, 

 if I remomber rightly, whero Mastodon 



Tapiro'ides and Binotlicrium are found. 

 The fragments do not fit together, but the 

 tusk seemed to be concave at the point 

 and a good deal curved. This specimen 

 has made me feel uncomfortable about 

 my inferences respecting the M. Tapi- 

 ro'ides origin of the tusk specimens I saw 

 at Zurich. There is not the least ap- 

 pearance when the cortical layer is 

 removed, of the sillons longihidiv'ales. 

 Can it be the incisor of Binotherium?' — 

 LEd.] 



