FALCONER MASTODON AND ELEPHANT. 313 



terms " broad-" and " narrow-ridged," instead of " thick-" and 

 " thin-plated " molars. 



The mammillary divisions of the ridges in the Mastodons, when 

 worn, form disks, i. e. a depressed surface of ivory, surrounded by a 

 raised rim of enamel ; and by the further progress of wear the sepa- 

 rate disks become confluent into larger disks, that are either trans- 

 verse or trefoil-shaped and alternate. In Eueleplias the divisions 

 of the compressed ridges form finger- or quill-shaped processes, 

 which at first are ground down into distinct " annular disks " ; 

 two or three of these then become confluent into a compound 

 oval disk ; and at length the separate oval disks run together, 

 forming a transverse band (" ruban " of Cuvier). Although it may 

 not be strictly logical to apply the term " transverse disks " 

 to these narrow bands (tgenise semidetritse), still they may be 

 regarded as very flattened ellipses ; and I have found it convenient 

 to use the term in this arbitrary sense in order to maintain a 

 uniformity of terms in designating the same object under different 

 modifications. 



The enamel plates furnish the most important distinctions. 1st, in 

 regard of the thickness : in E. primigenius they are only half as thick 

 as in E. meridionalis, and thinner than in the Indian Elephant or in 

 E. {Eiielephas) antiquus. 2ndly, surface-characters. The inner sur- 

 face, where in contact with the ivory, is usu.ally smooth ; and the 

 edges of the plates, in the worn disks, is even, whether the plates 

 are straight or plaited. The outer surface is rugous and uneven in 

 two directions : — 1st, vertically from parallel or divided ribs sepa- 

 rated by anastomosing channels, which are close-set and irregular 

 in size, and which are most marked below, disappearing upon the 

 apices of the digitations ; and 2nd, transversely, from parallel, wavy, 

 contiguous, and very frequent rugce or superficial puckering. In 

 the vertical section these communicate a ragged, feathered edge 

 to the outer surface of the plates ; while the transverse section of 

 the ribs and channels, in the worn plates, produces a spurious ap- 

 pearance of crimping, which it is important to distinguish from 

 plaiting or folding of the enamel upon itself. The undu.lated mar- 

 gins caused by these alternate ribs and channels multiply the tritu- 

 rating inequalities of the enamel, and they serve also, along with 

 the transverse puckers, to abut the cement firmly against the enamel 

 plates, and diminish its liability to splinter during the process of 

 trituration. This channelling is most strongly marked in the species 

 which have thick plates of enamel ; and when the plates are denuded 

 of cement, the ribs between the channels simulate the appearance of 

 cords. 3rd. Flexure of the plates transversely. This is presented 

 under two forms : first, primary flexures, where the plates are folded 

 upon themselves by numerous minute plicatures, closely applied to 

 each other, and communicating a continuous zigzag appearance to 

 the worn edge of the enamel, on both sides ; this is the character t(f 

 which Cuvier ap]flied the term "festooning," and here called 

 "crimping" or "plaiting"; second, secondary flexures, caused by 

 the outline of the ivory cores upon which the enamel plates are 



