Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/599

 interval between the postexternal (b) and the postinternal (d) lobes is not closed by a ridge descending from the summit of the postexternal lobe as in Chalicotherium sivalense * : nor does the inner side of the antexternal lobe terminate in so ridge-like a way as in Ch. sivalense ; it is more rounded. The inner side of the postinternal lobe (d) is rounded in Ch. sinense, not angular as in Ch. sivalense†. The following are admeasurements of the last molar (m 3') of the two species of Chalicotherium.

Admeasurements of the last Upper Molar.

Fore-and-aft diameter of outer side " " inner side in. lines. C. sinense. C. sivalense.

Falconer observes of the molars of Chalicotherum sivalense, " their width is greater than their length " (tom. cit. p. 192) ; but the direction of these dimensions is not defined. In Chalicotherium sinense, as in Ch. sivalense, the diameter from without inwards equals that from before backwards. In speaking of the length of a tooth, one ordinarily means the extent to which the crown projects from the socket ; and this is commonly the " vertical diameter " of the crown. In this sense the length of the molars of Chalicotherium is much less than their breadth, whether transverse or antero-posterior. But, then, this inferiority of length does not differentiate the molars of Chalicotherium from those of Anoplotherium. The length of the entire tooth in both genera, which includes the implanted part, is greater than any other diameter or dimension. The difference in the mineral condition of this Chinese cave-tooth and the fossil teeth of the same genus from the upper Miocene of France, Germany, and India is very striking and suggestive.

The older Chalicotherian molars, recognized by Kaup and Lartet, are truly petrified fossils. Those also from the Siwalik sands are in this state ; but Falconer remarks that, when clay is the matrix, the bones, and, we may presume, the dentine of the teeth, remain white, and, except in being deprived more or less completely of their animal matter, they have undergone little alteration (tom. cit.

follows : — " The apex of the posterior reentering angle gives off a like transverse ridge, which sweeps round into the posterior side." (Palaeontological Memoirs, 8vo, vol. i. p. 192).
 * This structure is noticed by the careful and minute observer Falconer, as

† The differential structure in Chalicotherium sivalense is noticed as follows, in the same useful and instructive summary of his scientific thoughts and works :— " This is the ' transverse ridge,' which is much inclined downwards and joins on with the isolated conical cusp (a, a', a") in the anterior and inner corner of the tooth, a cusp characteristic of Anoplotherium" (Falconer, Palaeontological Memoirs, vol. i. p. 192.) I may, however, remark that the conical cusp is equally characteristic of Paloplotherium, and, though of smaller size, of Hipparion.