Tertiary.-] PALAEONTOLOGY OF VICTORIA. [Mammalia. 



This tooth, by its large strap-shaped compressed fang, obviously 

 lateral and non-terminal in position in the jaw, and directed 

 upwards and backwards, belongs to the sub-genus Dolichodon of 

 Gray, and seems to differ from all the known ones in the abrupt 

 backward arching of the fang, bringing the tip down nearly to the 

 level of the base. The outer side is more convex than the inner, 

 and the concave posterior or inferior edge is thicker than the 

 convex anterior or upper edge, both edges being obtusely rounded. 

 There is no perceptible inward curvature, such as makes the 

 corresponding teeth nearly meet over the rostrum in some of the 

 living species. The rounded distal end and the relative obliquity 

 of the truncation of the base resembles the recent Z. (D.) Layardi, 

 but the tooth is relatively thicker and much more arched back- 

 wards. The denticle, or true crown of the tooth, has not been 

 observed, but doubtless surmounted the large pulp cavity on the 

 outer face of the distal end. A transverse section at 3 inches from 

 distal end shows the abrupt narrowing of the pulp cavity as in 

 Prof. Turner's figures of the living Mesoplodon Layardi, and the 

 naked eye, or a low power, shows in transverse longitudinal 

 fractures of this, as in that, the same proportions and disposition of 

 modified vaso-dentine, about 3 lines thick of which occupies the 

 middle of the shaft or fang, traversed by coarse flexuous branching 

 canals running nearly vertically ; outside this is a much denser 

 layer, from 1 J to nearly 3 lines thick, with much finer tubes directed 

 almost perpendicularly to the surface. On the surface is a very 

 thin layer of cement. 



It is curious that the three or four species of ear-bones or 

 Cetotolites found in the same beds near Geelong as these remains 

 of teeth and hard snout-bones of Ziphioid Whales exhibit rather 

 the type of those of the Balenoid Whales ; and the same happens 

 in the English Crag, where the great number of species of Ziphius, 

 determined by their snout-bones, are accompanied by 4 or 5 species 

 of ear-bones of Balena. 



In some thinner and shorter examples than that figured the 

 pulp cavity seems entirely absorbed, the middle being filled with 

 the modified vaso-dentine, with longitudinal small flexuous cylin- 

 drical canals, and the denser layer with much finer tubes perpen- 



DEO. vn. _ [ 25 ] D 



