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pulp ; it is bounded by the sharp edge of the shell of dentine that existed 

 at this period of formation, before the development of the fangs. 



From the tertiary deposits of Ohio. Purchased. 



737- The crown of the last molar tooth of the Mastodon giganteus, extracted 

 from its alveolus before the commencement of the development of the 

 fangs : it supports four bipartite transverse ridges and a posterior talon 

 supporting three large and three small tubercles. A portion of the first 

 ridge is broken away., but the summit of the remainder is entire, and 

 shows that it had not come into use. 



From the tertiary formations of Missouri. 



Presented by S. P. Pratt, Esq., F.R.S. 



738. A molar of the Mastodon giganteus further advanced in its development, 



the divisions of the fangs beginning to be formed : the base of the tooth 

 is still excavated by a single deep cavity for the lodgment of the pulp. 

 From the tertiary deposits of Ohio. Purchased. 



739. The antepenultimate molar, left side, lower jaw of the Mastodon giganteus, 

 the crown of which is divided into three transverse ridges, and an anterior 

 and posterior narrow transverse talon ; the enamel is abraded from the 

 summits of the mammilloid divisions of the anterior ridge ; the enamel 

 has been detached from a great part of the inner side of the crown 

 showing the direction of its fibres : the strong backward curvature of the 

 extremity of the anterior fang gives it an unciform figure. 



From the tertiary deposits of Ohio. Hunterian. 



740. A much-worn molar of the Mastodon giganteus, consisting almost en- 



tirely of fangs, nearly the whole of the enamelled crown being worn 

 away and excavated into a single cavity with a uniform polished surface 

 of dentine. 



From the tertiary deposits of Ohio. Purchased. 



741. A similar but still more abraded molar of the Mastodon giganteus, in 

 which some of the osseous deposition, ' osseo-dentine ', of the central 

 cavity of the fangs, forms part of the smooth and polished grinding 



