RHINOCEROS LEPTORHINUS. 



37i 



* Lyell's specimen partly mutilated. 



The next specimen is a third upper premolar, left side, the crown 

 worn very low down, so that the basal bourrelet is removed. The 

 posterior valley is reduced to a ' round pit,' and the central valley to 

 an isolated fissure, somewhat uniform in outline. 



Dimensions. — Width of crown, 1-8 in. Length outer side, 1'45 in. Length 

 inner ditto, V2 in. 



N.B. In general form this specimen resembles a good deal (fig 1 of 

 PL LI. 1 ) of the ' Ossemens Fossiles.' which is of the opposite side. In 

 the latter, which is of B. tichorhinus, and much worn, the posterior fos- 

 sette is much larger in proportion to the transverse fossette, and is less 

 round. 



The milk molar (PL XXXII. fig. 7) is in the finest state of preserva- 

 tion ; it has no fangs ; the crown is in the best stage of wear to show 

 all the characters. The angle formed by the crochet is very open, in 

 consequence of the obliquity of the disc of the posterior barrel ; there 

 is no basal bourrelet, but a rudimentary intercolumnar tubercle. The 

 groove of the external angle is deeply marked and broad, and the pos- 

 terior niche is also broad and well marked, overlapping the next tooth. 

 The crochet is undivided, and the outer ridge throws off a large soli- 

 tary combing plate, which is directed parallel to the anterior end of the 

 crown, and at right angles to the crochet, which it nearly touches. 

 The barrels are as fully developed as in a true molar, and but for the 

 small size the tooth would be fixed to be a fourth or last milk molar. 

 The outer vertical groove is very deep, and its posterior bounding ridge 

 very high and strongly developed. The posterior valley forms a gaping 

 triangular fissure, with shelving sides. It is of large size, the posterior 

 edge intact, and emarginate, so as to form a bi-lobed edge like the 

 carnassier tooth of a tiger. The transverse valley is very open at its 

 mouth, forming a triangular fissure. It is then bent gently forwards, 

 to terminate in the cul de sac. There is a small intercolumnar tubercle, 

 but not a trace of a basal bourrelet inside. The thick ' combing plate ' 

 is almost in contact with the point of the crochet. If they had run 



I together a third fossette would have been formed, as in the premolar. 

 The opening of the transverse valley is gaping, and the posterior barrel 



