MASTODON. 619 



is now in the Cabinet of the American Philosophical Society at 

 Philadelphia. Dr. Hays has refigured the specimen, as a lower jaw 

 of the Tetracaulodon, in his Memoir in the Transactions of the 

 Society for 1831. Why Cuvier should have suppressed the in- 

 structive plate of this lower jaw in his 2nd Edition of the 

 ' Ossemens Fossiles' I know not. The Plate 26 in Dr. Hay's 

 Memoir would indicate that both lower tusks were occasionally 

 retained in the male Mastodon giganteus as they commonly are in 

 the male Mastodon angustidens. 



227. M. angustidens. — The molar teeth of this extinct Europsean 

 Mastodon are narrower in proportion to their antero-posterior extent, 

 and their grinding surface is more mammillated and less transversely 

 ridged than in the Mastodon giganteus. As in this species the molar 

 series, on each side of the upper jaw and probably also of the lower, 

 includes two deciduous teeth which are succeeded by one tooth in a 

 vertical direction, and this by four other molars progressively in- 

 creasing in size, and pushing out their predecessors as they advance : 

 the total number of molars developed on each side of the upper jaw 

 being seven ; the greatest observed number in use, or exposed at 

 the same time is three on each side ; which is reduced in the old 

 animals to one on each side. 



The first milk-molar PI. 144, fig. 12, d 1,(1) has an oblong 

 subquadrilateral transverse section, rounded anteriorly : it is ob- 

 scurely quadricuspid ; the two anterior cusps are first blended 

 together by attrition, then the posterior external cusp is worn 

 down into the same surface ; the posterior internal cusp remaining 

 longest distinct. It has two fangs. 



The second milk-molar (ib. d 2) (2) is at least three times 

 as large as the first and supports three pair of cusps, the posterior 

 ones being the largest : and the outer one of the middle pair 

 indicates by its lateral projection the outer side of the tooth : a 

 narrower tuberculate ridge is developed at the anterior and pos- 

 terior margins of the crown. Each pair of cusps is reduced by 

 progressive attrition to a transverse oval depression, the two ex- 

 terior and posterior cusps being the last to yield. It has two 



(1) Kaup, ' Ossemens Fossiles de Darmstadt," PI. 16, fig. 1, & la, PI. 20, fig. 2. 



(2) Ibid. PI. 16, fig. 1, & la, PI. 17, fig. 12, PI. 21, fig. 1. 



