1857.] FALCONER^ — MASTODON. 339 



Lower jaiv. — The characters furnished by the lower jaw are of 

 great significance in distinguishing the nearly aUied species of Mas- 

 todoiiy more especially in what relates to the form of the symphysis 

 and the presence or absence of mandibular incisors. The diiferences 

 between the lower jaws of 3/. {TrilopJiodon) angustidens^ M. (Tetra- 

 loph.) loncjirostris, and M. {Tetratoph.) Arvernensis are so pro- 

 nounced, that they would have been sufficient to discriminate the 

 species, supposing the molar teeth were unknown to us. As above 

 stated, no good si)ecimen, so far as I am aware, has hitherto been 

 discovered of the lower jaw of the Crag species, M. (Tetr.) Arver- 

 nensis, in England ; but several have been met with in the Pliocene 

 strata of Italy and France ; while abmidant remains of the lower 

 jaw of M. {Tetraloph.) longirostris have been disinterred from the 

 Eppelsheim sands by Dr. Kaup ; and of M. {Trilophodon) angusti- 

 dens by MM. Lartet and Laurillard from the Falunian deposits of 

 the Sub-Pyrenees. 



First in regard to M. {Triloph.) angustidens. The lower jaw of 

 this species is at once distinguished by the great elongation, down- 

 ward direction, and slender form of the symphysial portion which con- 

 tains the sockets of the two inferior incisors*. The ascending ramus 

 is of moderate height, corresponding in that respect with M. (^Trilo- 

 phodon^ Ohioticus, and approaching that of Binotherium giganteum. 

 The horizontal ramus is very high in front, in a line with the men- 

 tary foramen, and low behind ; the anterior portion is compressed ; 

 and the lower margin stretches som.e way in front of the mentary 

 foramen, in a straight line ; it is then bent a little downwards, and 

 continued forwards in nearly the same straight line ; the under sur- 

 face of the elongated portion formhig an obtuse angle with the cor- 

 responding surface of the horizontal ramus. The elongation of the 

 symphysial beak is enormous, far exceeding that of M. {Tetralopho- 

 don) longirostins, or even of Dinotherium ; the length from the men- 

 tary foramen forwards being more than double that of the horizontal 

 ramus, measured from the same point backwards to the base of the 

 anterior margin of the coronoid process. A constant character of 

 the species is the presence in both sexes of two long, closely ad- 

 pressed, and straight, or but slightly curved, incisors. This fact has 

 been established by M. Lartet upon a very large number of speci- 

 mensf. 



These lower incisors differ notably in form from, the upper. In the 

 adult specimens they are nearly of uniform diiimeter from the base 

 to the point, which is bevelled on the upper side by v/ear, so as to 

 yield a flat or spathulate surface. In section they are pyriform, with, 

 frequently a longitudinal channel on the upper and inner side. The 

 section closely approaches that of the inferior canines of the fossil 

 Hippopotamus named Hexaprotodon Sivalensis. The tusks or upper 

 incisors of this species are nearly circular in section, and taper gra- 

 dually to a conical point. They are invested along their length on 

 the inner side by a broad band of enamel, which runs in an obsolete 



* De BIaiuv:lle, Osteographio : Des ElepLants, pi. li. 

 t Lurtet, Notice sur la Coliiue de Sausan, p. 2-1. 

 VOL. XIII. — FART I. . 2 B 



