CESTRA-CIOXTIDiE, 
327 
stouter and less elevated, and there are five denticles in front, while 
only three or four can be distinguished behind. In series ye. to ix. 
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 number, 
both in front and behind. In series x. the teeth are only about 
two thirds as wide as those of no. ix., while those of series xi. are 
still smaller by one half; and in both of these all the coronal pro¬ 
minences have become insignificant, though yet faintly indicated by 
a beaded contour. The base of the crown in all the teeth is 
marked by fine reticulating wrinkles, and the lower portion of 
the coronal cusps is often vertically striated. 
On comparing the teeth of this fossil with the few examples of 
S. dubrisiensis already described, one important difference will at 
once be noted. Whereas in Mr. Willett's specimen the most an¬ 
terior teeth are very small and delicate, some other fossils exhibit 
teeth in a corresponding position of a very large and robust cha¬ 
racter, with several feebly-marked denticles on each side 1 . One 
specimen noticed below (Xo. 41675) suggests that the latter per¬ 
tain to the upper jaw; and in that case the Brighton fossil may 
represent the lower dentition. There can be no doubt, indeed, that 
the two t}’pes belong to one and the same species; but whether the 
differences in the anterior teeth depend merely upon their pertain¬ 
ing to one or the other jaw, or whether one type is referable to the 
male and the other to the female, remains yet to be determined. 
The present writer has examined no specimen in which the small 
teeth and the robust teeth occur together. 
Synechodus dubrisiensis (Mackie). 
1863. Hybodus dubrisiensis, S. J. Mackie, Geologist, vol. vi. p. 241, 
pi. xiii. 
1886. Hi/bodus (?) dubrisiensis, A. S. Woodward, Proc. Zool. Soc. 
p. 218, pi. xx. 
1888. Synechodus dubrisiensis, A. S. Woodward, Proc. Geol. Assoc, 
vol. x. p. 288. 
1888. Synechodus dubrisiensis, A. S. Woodward, Geol. Mag. [3] 
vol. v. p. 496, woodcut. 
Type. Jaws with dentition ; British Museum. 
Supposed upper anterior teeth robust, the coronal surface promi¬ 
nently striated almost to the apex, and the lateral denticles three 
1 Proc. Zool. Soc. 1886, pi. xx. fig. 3 a. 
