218 FOSSTT. FTRTTES OF THE ENGLISH CHAEK. 



facoUc for a ])Ostoi'l)ital articulation Avitli tlic skull. '^I'lio niaiiilibular cartilage 

 (figs, (i, 7, iixL) is deepest just bencatli the liiiulcr end of its tooth-bearing' portion, 

 and gradually tapers to tlie blunt synipliysis, which is short. In the hyoid arch 

 the n})[)er or hyoniaudilndar element (fig. 7, Inn.) is comparatively small and 

 slender. The ceratohyal (fig. 7 n, <'hii.) is nnich larger and stouter, and expanded 

 at its distal or anterior end; at one third of its length from the proximal end its 

 lower border exhibits a prominent tuberosity (;r.), evidently for a muscular 

 insertion (see Proc. Zool. Soc, 1886, p. 222). 



The partially scattered teeth imperfectly shown in the type specimen belong 

 chiefly to some of the antero-lateral series, though there are also a few of the small, 

 narrow, beaded teeth of the hindmost series. One tooth (fig. Orr) seems to corre- 

 spond with those of the fourth series in the Avell-preserved dentition shown in PL 

 XLVI, fig. 1, and most of the others are easily comparable with various teeth in 

 the same specimen. This fossil may therefore be described as exhibiting the whole 

 of the dentition of one jaw of S. dnhrlsiensis. About 140 teeth are displayed in 

 their natural relative positions. There are eleven series on either ramus of the 

 jaw, each of those posteriorly placed comprising as many as eight or nine teeth, 

 while those near the symphysis have not more than six. The base of the crown in 

 all the teeth is marked by fine, reticulating wrinkles, and at least the lower portion 

 of the coronal cusps is vertically striated. The low root is flattened on its attached 

 face, though coarsely crimped along the outer border ; and, at least in the anterior 

 teeth, it projects beyond the inner face of the crown. There is no median symphy- 

 sial row of teeth, and the first pair (PI. XLVI, fig. 1, i) is extremely small. In 

 the latter the principal coronal cusp is long and slender, its height being equal to 

 the complete width of the tooth ; and there are two small denticles in front, one 

 behind. The teeth of series ii are nearly four times as wide as those of no. t, with 

 the principal coronal cusp still very prominent, and flanked in front and behind by 

 three large denticles and one small point, of Avliich those behind are the more widely 

 spaced. The teeth of series iii are vei-y similar to those of no. ii ; l)ut in the teeth 

 of series iv and v the principal cusp rapidly becomes stouter and less elevated, and 

 there are five denticles in front, while only three or four can be distinguished 

 behind. In series vi to ]X the size of the teeth only gradually decreases backwards, 

 but the principal cusp becomes very short and stout, thus more resembling the 

 lateral denticles, which are still very numerous and placed well apart. In these 

 teeth the denticles are five or six in nunil)cr, both in front and behind. In series x 

 the teeth are only about two thirds as wide as those of no. tx, while those of series 

 XI are still smaller by one half. In both of these the coronal prominences have 

 become insignificant, though yet faintly indicated by a beaded contour. 



The very small foremost teeth shown in the dentition just described have not 

 hitherto been observed in any other specimens. On the other hand, some of these 

 exhibit, in a corresponding position, comparatively large and robust striated teeth, 



