ELEPHANTID^l. 37 



Mastodon pandionis, Falconer r . 



Syn. Tetrabelodon pandionis, Cope 2 . 



In this species the mandibular symphysis is produced into a long, 

 deeply hollowed, trough-like expansion, which in some specimens is 

 edentulous, but in others (which are apparently specifically identical) 

 is furnished with a pair of large laterally compressed incisors 3 , the 

 mandibular rami being also compressed in the same direction. The 

 cheek-teeth are relatively wide, and are normally characterized by 

 the extreme complexity of the structure of the crowns, the accessory 

 tubercles being very numerous, placed on both sides of the median 

 longitudinal cleft, and completely blocking the valleys, although 

 in some earlier " intermediate " molars provisionally referred to this 

 species 4 the valleys are more free. The ridges are divided into 

 inner and outer columns, which have an alternate arrangement, and 

 when worn do not present distinct trefoils of dentine. The third 

 milk-molars provisionally referred to it are more complex than is 

 usually the case with trilophodont species, and in this respect agree 

 with those of M. penteliei ; the third upper true molar is relatively 



K». 7. 



? Mastodon pandionis. — The fourth right upper premolar ; from the Lower 

 Siwaliks of Dera Bugti, north-west frontier of India. j. Indian Museum, 

 Calcutta, No. A 432. (From the ' Palgeontologia Indica.') 



short ; and the enamel of all the teeth is thrown into vertical plica- 

 tions. It is probable that premolars were developed, at least in some 

 instances 5 , and a tooth provisionally so considered is figured in the 

 accompanying woodcut (fig. 7). 



1 Palseontological Memoirs, vol. i. p. 124 (1868). 



2 Proc. Amer. Phil. Soe. toI. xxii. p. 5 (1884). 



3 See ' Palaeontologia Indica ' (Mem. Geol. Surv. Ind.), ser. 10, vol. i. pi. xxxv. 

 and Cat. Siwalik Vert. Ind. Mus. Calcutta, pt. i. pp. 99-101 [1885]). 



4 ' Pakeontologia Indica,' ser. 10, vol. iii. p. xx (1888). 5 Loc. cit. 



