RHINOCEROS LEPTORIIIXUS. 383 



the last premolar, left side, Lad never emerged, or that it had dropped 

 out after emergence. (On subsequently removing the outer alveolar 

 wall it was visible.) 



The basal bourrelet, as a general rule, is but indistinctly exhibited in 

 all the premolar teeth of this specimen. 



5. The antepenultimate true molar {or t.m. 1). — This tooth is present 

 in a more advanced state of wear than either p.m. 2, 3, or 4, the stage 

 of detrition being about the same as in De Christol's fig. 18 (copied 

 in PI. XVIII. fig. 3), but even a little more advanced. The crown of the 

 tooth had originally been quite entire in this specimen, but it had got 

 crushed and shivered ; the pieces have been replaced in position with 

 glue. The posterior fossette and the whole of the middle valley are 

 enveloped by matrix, so that the offset of the crochet is entirely con- 

 cealed, as is the greater portion of the inner side of the two barrels. 

 The anterior basal talon bourrelet is very pronounced, with a crenated 

 margin. The corresponding tooth of the opposite side (left) is also 

 present, and still more perfectly conserved ; but the crown is nearly 

 entirely enveloped by matrix, so that the characters yielded by the 

 crochet are not visible. 



6. The penultimate (or t.m. 2), right side. — This tooth is present 

 and quite perfect, but is pressed slightly inwards upon the palate. The 

 outer shell of enamel is seen to be quite perfect, and the outer ridge 

 but very slightly abraded, the boundary of the posterior fossette being 

 quite entire. The anterior barrel has its edge but slightly abraded, a 

 little more in degree than p.m. 4 ; the whole of the central valley and 

 of the inner sides of the barrels are enveloped by matrix, so that the 

 form and offset of the crochet and the anterior basal talon are com- 

 pletely concealed. This concealment of the most characteristic part of 

 the crown is much to be regretted for my present purpose. The corre- 

 sponding tooth of the opposite side is also present, but fractured and 

 repaired ; it is slightly dislocated outwards (like the whole of the series 

 of the left side), exposing completely the inner side of both barrels, 

 down to their base. There is not the slightest trace of an internal basal 

 bourrelet, and the summits of the barrels, more especially the hind one, 

 show very markedly the peculiar twist seen in fig. 18 of De Christol's 

 plate (as copied in PL XVIII. fig. 3). This character is equally seen 

 on the corresponding parts of p.m. 1, left side. 



7. The last true molar (t.m. 3) of the right side had not emerged, 

 and there is not a trace even of its presence, the corresponding alveolar 

 part of the maxillary bone being crushed in and covered by matrix ; 

 but, as will be seen in the sequel, the germ of this tooth is distinctly 

 present on the left side. 



B. Left Side. — 1. The pre-antepenldtimate, or (p.m. 1). — The single- 

 fanged alveolus of the first premolar is present, as in the opposite side, 

 distinctly defined, and partly occxipied by matrix. 



2. The antepenultimate, or (p.m. 2). — The crown of this tooth is 

 present, quite perfect, and but very slightly affected by wear. In a 

 general way it resembles very closely fig. 1 of Gervais' PI. II. ('Paleon- 

 tologie Francaise'), with the exception that the basal bourrelet, which 

 is distinctly present upon the anterior barrel, is less pronounced on the 

 posterior barrel than seen in that figure. The crown has a similar 

 sub-triangular form, i.e. broad externally, and contracting inwards. 

 The apex of the anterior barrel, which is all but intact, forms an 



