1857.] FALCONER MASTODON. 313 



the second or penultimate true molar, being three teeth in im- 

 mediate contiguity, in all the species (with one remarkable excep- 

 tion) are severally characterized in both jaws by an isomer oiis divi- 

 sion of the crown into either 3 or 4 ridges. These three isomerous- 

 ridged teeth may, for convenience of description, be referred to in 

 the aggregate as " the intermediate molars," a term which has been 

 applied to them from their position by Fischer and by Laurillard*. 

 To the species which present the ternary-ridged formula we have 

 assigned the subgeneric name of Trilophodon'\ ; and to the quater- 

 nary-ridged species, TetralophodonX. In citing the various forms 

 under discussion in the sequel, these subgeneric terms will, in every 

 case, be used for convenience in designating the species ; and the 

 same rule will be followed with the subgeneric divisions of Elephas. 

 This will be of obvious use on the present occasion, both as a help to 

 the memory in dealing mth a large number of specific names, and as 

 suggestive of broad points of distinction, when referring to the dis- 

 puted species. 



The ternary and quaternary formulae are, I believe, never found 

 mingled in the intermediate molars of the same species § ; i. e, a. 

 ternary-ridged molar of this series does not occur in the species be- 

 longing to Tetralophodon, nor a quaternary in Trilophodon. The 

 ridge-formula indicates also, with unerring certainty, the composition 



* Dictionnaire Universe! d'Histoire Naturelle, torn. viii. p. 29. 



t From rpels et Xo^os, three-ridged. 



X From reaaapa et XScpos, four- ridged. This difference of three and four ridges 

 was, so far as I am aware, first pointed out as a distinctive character between two 

 European species, namely Mastodon angustidens and Mastodon Arvemensis, by 

 Von Meyer as far back as 1834, but without being extended to the three inter- 

 mediate molars. The name Mastodon Arvemensis was applied by him to the 

 Eppelsheim species. Mastodon longirostris of Kaup. (Die Fossilen Zahne und 

 Knochen von Georgensgmiind, p. 33.) The ridge-formula in the two subgenera is 

 as follows : — 



Milk-molars. True molars. 



T rr -1 V J 1+2 + 3 3 + 3 + 4 



In Trilophodon 



In Tetralophodon 



1+2+3 3+3+4 

 2+3+4 4+4+5 



2+3+4 4+4+5 



the numerals exhibiting the ridges in each tooth, exclusive of the " talons." 



§ The only apparent exception which has come under my observation, occurs 

 in the dentition of the South American species, to which the name of Mastodon 

 Andium (Tetralophodon of our arrangement) has been restricted by the French 

 palaeontologists, Laurillard and Ger^ais, as distinct from M. Humboldtii (Trilo- 

 phodon). In this species the last ridge in most of the intermediate molars is con- 

 siderably reduced in size ; and the teeth have been, in consequence, described by 

 Gervais (Zoologie de I'expedition dans TAmerique Meridionale par Le Comte 

 de Castelnau, p. 19) as three-ridged. The specimens represented by him, figs. 2 

 and 5 of pi. 5 in the ' Voyage de Castelnau,' the former an antepenultimate upper 

 true molar, and the latter a penultimate lower, are distinctly four-ridged, while the 

 last lower milk-molar, fig. 4, is apparently three-ridged, with a large talon. My 

 attention was directed to the subject by M. Lartet. More specimens are required 

 for the exact determination of the point than yet exist in any of the European 

 museums ; i. e. whether in the intermediate molars of the form called Mastodon 

 Andium the ternary and quaternary formulae are mingled. Nine-tenths at least of 

 the specimens of South American Mastodons in the British Museum belong to 

 the other species, M. {Trilophodon) Humboldtii. — July 1857, H. F. 



