398 THE MEDALS OF CREATION. Crap. XI. 
noticed below the Lias, in which formation one very re- 
markable species is so abundant as to be considered charac- 
teristic of the Liassic deposits. It is so faithfully represented, 
Lign. 127, fig. 6, that description is unnecessary. In the — 
upper argillaceous beds of the Oolite and Kimmeridge 
Clay, a very small gryphite, (G. virgula, Ly. p. 260) is 
so abundant, that it constitutes entire layers. The low 
cliffs on the west of Boulogne harbour, like those near 
Weymouth, are composed of this clay, and myriads of the 
gryphites are scattered on the shore, with other shells of 
the same deposits; these shelly beds are called marnes & 
gryphées, by the French geologists. _ A very large gryphite, 
Gryphea sinuata, (Min. Conch. tab. 336,) is found in the 
Shanklin sand of the Isle of Wight, and of Kent and 
Sussex. At low water, in the sand along the shore under 
Dunnose Cliff, near Shanklin Chine, numerous specimens 
are always obtainable.* 
SponpyLus. ign. 128.—A species of this genus is so 
frequent in the Chalk, that it ranks with certain Terebra- 
tule, as characteristic of that formation. One valve is 
covered with long slender spines, which, in the usual 
examples, are destroyed by the mode of extracting them. 
The specimen figured shows the appearance of a shell partly 
cleared ; the remainder of the chalk might be removed by 
a pen-knife (taking care to leave the longest spines sup- 
ported by brackets of chalk), and it would then resemble 
the beautiful fossils figured Min. Conch. tab. 78, and in 
Geol. S. H.p. 125. Between the beaks there is a triangular 
aperture in the spinous valve, which some naturalists, with 
much probability, suppose was once filled up with shell, as 
in the recent species. 
* The name Exogyra was applied to the Chama-shaped species of 
Gryphea by the late Mr. Sowerby, and other writers; but subsequent 
authors have included these shells in the present genus. 
