38 BRITISH AND EUROPEAN FOSSIL MASTODONS. 



(Trilophodon) angustidens. 1 In a manuscript note appended 

 to the work here quoted, with which I have been favoured 

 by M. Lartet, he adds, ' J'ai pu depuis lors verifier plusieurs 

 fois le remplacement effectif de la 2 me et de la 3 me molaire de 

 lait, tant a la machoire superieure qu'a l'inferieure comnie 

 cela a lieu dans le Dinotherium ; la premiere n'est jamais 

 remplacee.' In a beautiful specimen of the lower jaw of a 

 young M. (Trilophodon) angustidens, belonging to M. Ziegler- 

 Ernst of Winterthur, I found both the penultimate and last 

 premolars present — the former protruded, the latter in germ. 

 When a single premolar is developed, it is the successor to 

 the last milk molar, and not to the penultimate, as stated by 

 Prof. Owen in the passages above referred to. 2 I have 

 seen detached specimens of this last premolar, both of the 

 upper and lower jaws of M. (Tetralophodon) longirostris of 

 Eppelsheim, in the Museum at Darmstadt. The order of 

 succession here indicated is alone consistent with what occurs 

 in other Pachyderms, where, when suppression in either of 

 the milk or premolar series takes place, it is constantly the 

 anterior or feebly developed and rudimentary teeth that are 

 suppressed. In them we never find the last premolar sup- 

 pressed while the penultimate is developed, but the reverse. 

 The ijenultimate premolar replaces only the corresponding 

 milk molar : the antepenultimate milk tooth is never re- 

 placed in Mastodon or Elephas so far as observation has yet 

 shown. The molar dentition of the permanent or second 

 set (i.e. the premolars and true molars) in M. (Triloph.) 

 angustidens and Dinotherium is numerically identical, con- 

 sisting of two premolars and three true molars; each of 

 these having also two well-developed mandibular tusks : and 

 the close affinity thus indicated by the number of teeth is 

 further borne out by the correspondence of a ternary -ridged 

 formula in two of their ' intermediate molars,' and by other 



1 Lartet, 'Notice sur la Colline de 

 Sansan'(1851), p. 25. 



In his subsequent memoir on the 



molar teeth of Phacochcsrus, &c. (Phil. 

 Trans. 1850, p. 496), Professor Owen 

 takes a different view of the premolar 

 teeth in Mastodon from that set forth in 

 the ' British Fossil Mammalia ' and the 

 ' Odontography.' It is expressed thus : — 

 ' The existing species of the gigantic 

 Proboscidean family, viz. the Asiatic and 

 African Elephants, are totally devoid of 

 incisors in the lower jaw, and all their 

 grinding teeth succeed each other hori- 

 zontally; so that it is only by a more 

 than proportional increase of size that 

 the antepenultimate grinder is recogni- 

 zable as the first of the true molar series, 



and the antecedent smaller grinders, as 

 the homologues of the milk molars of 

 other Diphyodonts, which milk molars 

 have no successors in the Elephants. In 

 certain Mastodons, however, which are 

 the earliest known forms of the Probos- 

 cidean family, the last milk molar was 

 displaced by a vertical successor or pre- 

 molar.' The tooth, which, in his earliest 

 descriptions, was considered as the suc- 

 cessor of the antepenultimate and pe- 

 nultimate (first and second) milk molars, 

 is here regarded as the successor of the 

 last milk molar. But the presence of 

 both the penultimate and last premolars 

 in Mastodon angustidens is not recog- 

 nized. 



