88 FAUNA ANTIQUA SIVALENSIS. 



lower jaw differ in no important respect from tliose of the 

 upper, except in being narrower in proportion to their 

 length, and in the greater development of the anterior and 

 posterior subordinate talon ridges. 



With respect to the premolars, the statements which have 

 been advanced regarding them are conflicting. They have 

 never been observed in either of the jaws by Godman, Hays, 

 Cooper, Harlan, or any other of the American naturalists 

 who have described the dentition of M. Ohiotieus ; nor has 

 their presence been noticed by Dr. Grant. But Professor 

 Owen, in his ' British Fossil Mammalia,' affirms that they have 

 been recognized in this species ; and in his ' Odontography,' ^ 

 he figures and describes a tooth as the penultimate premolar 

 of the upper jaw. It is there stated to be composed of two 

 bifid transverse ridges, girt by a basal cinguluni, and to be 

 of a simpler form than the second deciduous molar; the 

 crown being broader in proportion to it* length, and mea- 

 suring one inch five lines, by one inch four lines. 



Professor Owen also gives a figure of the hypothetical 

 position of the same tooth in the lower jaw,^ the presence of 

 which he admits has not yet been established in the species. 

 The accurate determination of this point is of considerable 

 systematic importance, as the occurrence of this premolar 

 constitutes one of the two characters uj)on which (failing 

 those advanced by Cuvier) Professor Owen fovuids his generic 

 distinction between Mastodon and Eleplms. Had the tooth 

 been observed in situ in the jaw, as in the Dax SiDCcimen of 

 M. angusticlens figured by Cuvier, and in the specimens of 

 M. longirostris figured by Kauj), its occasional presence in 

 the upper jaw of 31. Ohiotieus would have been placed beyond 

 doubt ; but the tooth described by Professor Owen appears 

 to have been a detached specimen, and no characters are 

 attributed to it inconsistent with its being the first milk 

 molar of the upper jaw. In order to arrive at a certain 

 determination of the point, we have been permitted to make 

 a section of a sj)ecimen consisting of the entire palate of a 

 young Mastodon Ohiotieus in the British Museum, containing 

 the second and thh-d milk molars, with the first true molar 

 protruded and the second true molar in germ. A section 

 was made both along the palate, and along the outside of 

 the jaw ; but not a trace of a premolar was visible, although 

 the cranium was exactly of the age when a premolar, if 

 developed, ought to have been shown. A similar negative 

 result attended a corresponding section of a specimen of the 

 same age of the lower jaw. The only other evidence which 



> Loc. cit. p. 260. PL 144, fig. 3, y. 1. ^ Ibid. PL 144, fig. 7, p. 1. 





