BKITISH AND EUROPEAN FOSSIL MASTODONS. 



ridged species, Tetralophodon. 1 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 pre- 

 sent occasion, both as a help to the memory in dealing with 

 a large number of specific names, and as suggestive of broad 

 points of distinction, when referring to the disputed species. 

 The ternary and quaternary formulae are, I believe, never 

 found mingled in the intermediate molars of the same 

 species ; 2 i.e., a ternary-ridged molar of this series does not 

 occur in the species belonging to Tetralophodon, nor a qua- 

 ternary in Trilophodon. The ridge-formula indicates also, 

 with unerring certainty, the composition of the crown of the 

 tooth which is immediately in front of, and of that which is 

 immediately behind, the three intermediate molars : the 

 former showing invariably one ridge less, and the latter one 

 ridge more ; that is to say, the penultimate or second milk 

 molar in all the species- of Trilophodon is invariably two- 

 ridged, and the last true molar four-ridged ; while in Tetra- 

 lophodon, in like manner, the former is three-ridged, and the 

 latter five-ridged — making due allowance in the last true 

 molar for the amount of individual variety presented by the 

 greater or less development of the well-known talon compli- 

 cation, and for its being usually more complex in the lower 



as distinct from M. Humholdtii (Trilo- 

 phodon). In this species the last ridge 

 in most of the intermediate molars is 

 considerably reduced in size; and the 

 teeth have been, in consequence, described 

 by Gervais (Zoologie del' expedition dans 

 l'Amenqiie Meridionale par Le Comtede 

 Castelnau, p. 19) as three-ridged. The 

 specimens represented by him, figs. 2 

 and 5 of Plate v. in the ' Voyage de Cas- 

 telnau,' the former an antepenultimate 

 upper true molar, and the latter a penul- 

 timate 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 speci- 

 mens are required for the exact determi- 

 nation of the point than yet exist in any 

 of the European museums ; i.e., whether 

 in the intermediate molars of the form 

 called M. 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 



' ' From TeWapes and \6<\>os, 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 Mas- 

 todon angustidens and M. Arvernensis, 

 by Von Meyer, as far back as 1834, but 

 without being extended to the three 

 intermediate molars. The name M. 

 Arvernensis was applied by him to 

 the Eppelsheim species, M. longirostris 

 of Kaup. (Die Fossilen Zahne und 

 Knoehen von Georgensgmiind, p. 33). 

 The ridge-formula in the two subgenera 

 is as follows : — 



In Trilophodon 



Milk molars True molars 

 1+2+3 . 3+3+4 

 1+2+3 3+3+4 



t rr A i r. j 2 + 3 + 4 4 + 4 + 5 



In Tetralophodon ^^ : j^^ 



the numerals exhibiting the ridges in 

 each tooth, exclusive of the 'talons.' 



2 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 arrange- 

 ment) has been restricted by the French 

 palaeontologists, Laurillard and Gervais, 



1857, H. F. (See p. 15, note 3, and 

 also vol. i. p. 106. — Ed.) 



