The second specimen consists of a smaller proportion of the inner part of a penultimate or antepenultimate molar, with evidence of the notch or valley penetrating from the hinder side of the crown. The promontory, running from the postinternal lobe into the valley entering from the inner side of the crown, resembles in simplicity of form that of the preceding tooth. The ridge at the back part of the base of the postinternal lobe is likewise very thick. A small mammilloid process projects near the entry to the valley e. The bases of the two inner fangs are preserved.
A first molar (m 1), abraded to the base of the crown, agrees in size and in so much of character as is preserved with the foregoing specimens ; it exemplifies that of the valley e, inasmuch as, although the terminal bed is brought to the level of the grinding-surface, it is not insulated. The outer side of the tooth is broken away.
The outer enamel-wall (PI. XXIX. fig. 3), with a small portion of adherent dentine, of a fourth upper molar, not forming part of any of the other three teeth, shows a strong vertical columuar bulge (a) terminating at the apex of the antexternal lobe, as in Rhinoceros sumatranus; but it also has a second, well defined, but less prominent, vertical ridge (b) rising to the apex of the postexternal lobe, the two ridges dividing the outer surface of the crown into three facets. In Rhinoceros sumatranus this character distinguishes the premolars from the true molars; but the second or hinder ridge of the outer enamel-wall is less defined in that species; and in the present tooth the middle facet is not uniformly concave from before backward, but undulates, through the projection, near the hinder boundary ridge, of a lower longitudinal rising of enamel. The apices of the two outer lobes (a, b) are more prominent than in Rhinoceros sumatranus ; and the angular contour of that border of the tooth makes a closer resemblance than in Rhinoceroses generally to the outline of the same part in Paloeotherium.
The fossil upper molars of the species of Rhinoceros from Ava, figured by Clift*, are much worn ; but, as in the Chinese molar in the same condition, the closed and somewhat deeper end of the valley (e) is not insulated, as it is in all the Siwalik kinds at the same stage of attrition. The Avan teeth, however, indicate a larger animal than the Chinese species, and are more satisfactorily differentiated by the absence of the second longitudinal ridge (Pl. XXIX. fig. 3, b) on the outer wall of enamel.
Prom Rhinoceros platyrhinus, Fr.†, the Chinese species differs, both in the contour of the outer wall of the upper molar, and in the simplicity of the promontory. From Rhinoceros sivalensis, Rh. sinensis differs in the contour of the outer wall, in the thicker or broader promontory, and in the more uniform depth of the valley (e), whereby its termination is not insulated as in the specimen figured in pl. 75. fig. 5 of the ' Fauna Antiqua Sivalensis.' The same differences forbid a reference of the Chinese upper molars to Rhinoceros paloeindicus ; and both this and the Rhinoceros sivalensis were
- Trans. Geol. Soc. second series, vol. ii. pl. 40. fig. 1.
† Fauna Antiqua Sivalensis, pl. 72. Fig. 6.
VOL. XXVI. PART I. 2 G
