TYPES OF MOLAR TEETH OF MAMMALIA EDUCABILIA. 



83 



6. Bathmodont type. — I knoAV of no genus which by its intermediate structure 

 connects this type of molar with the Amoebodont form of Bunodonts. Such will 

 doubtless be discovered, for it is impossible that the upper molar of Bathmodon 

 could have been produced by the modification of any known Palseotheriodont, the 

 type which it most nearly resembles. The structure of the feet of the animal 

 forbids any such supposition. Such intermediate types would have, firstly, the 

 (oblique) crests more nearly equal in length and similar in direction. A depression 

 of the crests and indication of diagonal ridges connecting the tubercles in the 

 opposite direction would produce an approach to a W, and the form of Hi/opsodiis. 

 That this was probably the history of this curious type is rendered probable by 

 the form of the mandibular teeth, which exhibit two of the intermediate stages 

 above anticipated. Thus the last inferior molar exhibits two obliquely transverse 

 crests of subequal length, 

 with rudimental oblique or 



Fis. 27. 



diagonal ridges connecting 



BatJimoclitii. 



them. In the median lower 

 molars one of the latter is 

 developed, giving a V, as in 

 PaJceotherium, but the pos- 

 terior one is undeveloped, 

 leaving only the original 

 oblique cross-crest.* 



7. The Loxolophodonts. — Like the preceding group I know of no type connect- 

 ing this form with the Bunodont, but anticipate the discovery of a type with a 

 rudimental posterior V on the upper molars, which shall connect it with the W- 

 shaped type proposed above as the probable predecessor of Bathmodon. Or, a pair 

 of oblique parallel crests with rudimental diagonals like the posterior lower molars 

 o{ Bathmodon may intervene between this form and the Bunodont. This is, how- 

 ever, not probable in view of the 

 diagonal crest of the upper mo- 

 lars (Fig. 28, Uintatherium ro- 

 bust urn), and especially if the 

 parallel with the type of the 

 lower molars is kept up. These 

 are like those of Bathmodon, ex- 

 cept that the type of the middle 



FifT. 29. 



See Proceed. Amer. Philosophical Society, Sept. 1872, "On the Dentition of Metalophodon." 



