TRANSACTIONS OF WAGNER 



18 



MASTODON 



cessory tubercles, more or less well marked, spring from the base of the non- 

 buttressed lobes, contiguous to the buttresses of the other lobes, and to a 

 variable degree contribute to obstruct the middle of the transverse valleys of 

 the crown. 



In the worn condition of the molar teeth of M. floridanns, the exposed 

 dentinal areas of the specially buttressed lobes assume a more decidedly 

 trilobate and quadrilobate form than in J/. amcricanus, as seen in plate ii. 

 figs, i and 2, and as is also the case in the South American Mastodons. In 

 the opposite or non-buttressed lobes, the exposed enamel islets assume in 

 general a transversely elongated elliptical form. 



Professor Cope has described the molar tooth of a Mastodon from Texas, 

 which he refers to a previously undescribed species with the name of Tetra- 

 belodon serridens. In speaking of M. floridanns he remarks that its molars 

 present the same tubercular crests of the T. serridens, and no important 

 character appears to separate it from the latter. Though the tooth of M. 

 serridens bears a general resemblance to the corresponding molars of M. 

 floridaiuts, as do those of M. angnstidcns and some other species, it is 

 sufficiently different to render it probable that it pertains to a distinct species. 

 Professor Cope says it is peculiar among American species in its acute, elevated, 

 entire crests, with tuberculo-serrate edges. If by entire crests is meant that 

 they continue at a level across the crown, the condition will not apply to those 

 of M. floridanus, in which the constituent lobes, together forming the crests, 

 are separated by variably deep notches. In comparing the tooth with those 

 of M. titricensis, Professor Cope says it differs in having well-developed longi- 

 tudinal crests at the inner half of the external half of the crests, which consist 

 of two tubercles on the posterior sides of the crest and one on the anterior 

 sides of the next succeeding crests. In the molars of M. floridanns the cor- 

 responding longitudinal crests are usually divided into a greater number of 

 tubercles. Further, in Professor Cope's illustration of the tooth, accompanying 

 the description, the outer back lobe is represented with a conspicuous ridge, 

 sweeping in a bold curve from its summit backward and inward behind the con- 

 tiguous inner lobe. Such is not the case in any of the molars of M. floridanns, 

 in which, generally, the posterior offset of the last outer lobe of the lower 

 teeth, last inner lobe of the upper teeth, is not produced as in the lobes in 

 advance, and is always isolated from the conspicuous tubercular process pro- 

 jecting from the basal ridge at the back of the crown. 



The upper first and second true and the last deciduous molars of M. 



