208 PROCEEDI^"GS OF THE GEOLOGICAL SOCIETY. [Jan. 8, 



S. W. King. The jaw in which the former of these is implanted is 

 described by Dr. Falconer*. These two specimens afford insufficient 

 data for describing the milk-molars ; and therefore I will pass on at 

 once to the true molar series. 



The upper true molars of Rhinoceros Mruscus are defined at sight 

 from those of any other British species by the lowness of their 

 crowns, the abruptly tapering form of the colles t, d and e, and the 

 stoutness of the guard, o, on the anterior aspect. The grinding- 

 surface of the crown is deeply excavatedj as in the Leptorhine and 

 Megarhine teeth, instead of being worn flat, as in the Tichorhine ; and 

 the enamel is remarkable for its smoothness. For the British type 

 of the species I have chosen the molar series found in the Forest-bed 

 at Pakefield (Pls.YII. figs. 1, 2, and YIII. fig. 4), in which all the teeth 

 are present except the first premolar of the lower jaw. It belonged 

 to a Bhinoceros rather past the meridian of life. It is coYered with 

 a red ferruginous matrix, locally termed " pan," which is character- 

 istic of fossils which have been imbedded in the Praeglacial deposits 

 of the east coast. The first of the premolars (PL YII. figs. 1, 2) is 

 remarkable for the stoutness of the guard, o, that runs round the 

 anterior and inner surfaces of the crown, forming a clearly defined 

 step from its passage round the median coUis, e, to its upward sweep 

 at the point on the anterior aspect where the anterior collis, d, joins 

 the lamina. Its horizontal position up to that point is characteristic, 

 and defines the tooth from any of its Pleistocene or recent homo- 

 logues. Its antero- external angle is slightly produced. Gestae 1 and 

 2 are slightly developed, while costa 4, bounding the tumid posterior 

 area, is sharp and well defined. The second premolar, pm. 3, re- 

 produces all the characters of the first, excepting the production of 

 the antero -external angle. It is very much larger, and presents an 

 outline more nearly approaching an oblong. The tumidity also at 

 the base of the posterior area, n, is more pronounced. The third 

 premolar, pm. 4, is differentiated from the second only by its greater 

 size. The horizontahty of the guard, o, and its height above the 

 cingulum, characterize the whole of the premolar series, and prevent 

 its being confounded with that of any other British species. The 



*■ " Bhinoceros . Left ramus, lower jaw, five teeth out, last true molar 



not protruding, last milk-molar not dropped out, showing symphysis and dia- 

 steme ; longitudinal striae well marked ; matrix of ' red pan ' of forest-bed well 

 marked. Length from anterior end of socket of first premolar (dropped out) to 

 end of last true molar 10 inches," (Dictated to the Eev. S. W. King by Dr. 

 Falconer.) Dr. Falconer, however, seems to have made up his mind afterwards 

 as to its Etruscan character. See Palaiont, Memoirs, vol. ii. p. 347, published 

 after this essay was written, 



t A list of the terms and letters used to identify homologous parts in the 

 teeth of Rhinoceros has already been given, in the Quart. Journ. Geol. Soc. 

 vol, xxiii, p. 218. Without the use of some such system it is impossible to 

 assign a true value to the differences observable between closely allied species of 

 the same genus. Throughout the essays on the dentition of Ehinoceros, the 

 same terms and letters are used, so that the homologous parts in any one tooth 

 may be compared with those of any other. Most of the terms are taken from 

 the masterly work on the Tichorhine Rhinoceros by Professor Brandt (Mem. 

 Acad. St, Petersb. 6*^ ser. torn. vii.). 



