ON A NEW GENUS OF EXTINCT MAMMALS 



159 



The ci*mn of the entire tooth is bilophodont, and, as to its 

 central portion, saddle-shaped — its lobes, nearly equal in size, for.n 

 each a low cusp, rising fore and aft with a gently concave surface to 

 the central transverse line, on which is developed a low rather 

 s harp, level and trenchant crest. The subpyramidal anterior end 

 of the tooth from the crest forward is gradually contracted as it is 

 produced over the space separating the tooth at the base from the 

 one before it — the contraction ceasing, a smooth and regular tract 

 surrounds, as a collar, the end of the process, on which is formed 

 anteriorly a smooth oval surface directed downwards and backwards 

 to be applied to a similar face (reversely directed) on a much 

 shorter projection from the back of the hinder lobe of the antecedent 

 tooth. The beak like process of the broken tooth is still more 

 elongate. On the posterior surface of fracture there is exposed the 

 transversely compressed and closed fang of the front lobe of the 

 broken tooth — anteriorly the fracture passes through the hindmost 

 socket of the hindmost of the lost teeth, and shows that the fang 

 oteupying it was also single and compressed. 



From these data the following name and characters of the 

 genus may be deduced : — 



Synaftocion n.g. joss. Fam. Mac < podida — Molars rooted, 

 antibilophodont, distant at base, in contact by facetted projections 

 fore and aft. 



The only specific character that can be given is one of Jimerr- 

 sions. 



Synaptodon cevortim — The perfect tooth is i* mm. in length ; 

 5 mm. in its greatest breadth. The space between the teerh is 

 nearly equal to the length of each fore lobe. 



The mammalian origin of the fossil, which shows on its outer 

 side the commencing convexity of the base of the ascending process, 

 requires no demonstration. The facies of its teeth conspires with 

 its geological associations to suggest its marsupial derivation: and if 

 such source be assumed its bilophodont structure compels us to rt-fer 

 it to one of the herbivorous or semiherbivorous familiei of the order. 

 Lastly, if the longitudinal processes of the teeth may be considered 

 to be as they in all probability aie, modifications of basal talons, we 

 cannot be far wrong in associating the extinct genus with the family 



