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725. The last upper molar of the Mastodon giganteus, in which the three an- 

 terior bimammillary ridges of the crown have been abraded by mastication, 

 and the whole of the inner surface of the tooth worn away and polished 

 by some accidental circumstance connected with the stratum in which 

 the tooth was imbedded. 



From the tertiary deposits of Ohio. Purchased. 



726. The last molar of the right side of the lower jaw of the Mastodon gigan- 

 teus : the crown supports four transverse ridges with an anterior narrow 

 talon and a posterior broader and trituberculate talon : the crown is sup- 

 ported by three fangs ; the anterior one is of great breadth, compressed 

 from before backwards, and slightly carved backwards ; the second is the 

 smallest ; the third is a large conical mass partially subdivided by the 

 vertical grooves into buttress-like processes, corresponding with the 

 three posterior ridges on the inner side of the crown. A portion of the 

 anterior fang has been removed and the surface polished to show the 

 compact dentine. 



From the tertiary deposits of Ohio. Purchased. 



727. A similar but larger lower molar of the Mastodon giganteus : the crown 



supports five transverse ridges and a small posterior trituberculate talon: 

 the ridges decrease in breadth and height as they approach the back part 

 of the molar : they are each divided, as usual, into two mammilloid pro- 

 cesses, from which the name of the genus is derived ; the bottom of the 

 interspaces of the ridges is occupied by a dense substance of the same 

 dark chocolate colour as the cement which invests the fangs : the anterior 

 fang and a great part of the anterior ridge of the crown which it supports, 

 have been broken off. 

 From the tertiary deposits of Ohio. Purchased. 



728. The last molar of the right side of the lower jaw of the Mastodon gigan- 



teus. It has been longitudinally and vertically bisected. The crown sup- 

 ports four transverse ridges and a large posterior talon consisting of one 

 large udder-shaped process and four smaller mammillae. The cut surface 

 of the tooth shows the thickness of the enamel and the direction of its 



