(See Phillips' Geology of Yorkshire.) Some of the larger species equal a man's wrist in diameter.[1]
Scaphite.
The Scaphites constitute a genus of Elliptical chambered shells, (see Pl. 44, Fig. 15, 16,) of remarkable beauty, which are almost peculiar to the Chalk formation; they are so rolled up at each extremity, whilst their central part continues nearly in a horizontal plane, as to resemble the ancient form of a boat; whence the name of Scaphite has been applied to them.[2]
It is remarkable that those approximations to the structure of Ammonites which are presented by Scaphites and Hamites, should have appeared but very rarely, and this in the lias and inferior oolite,[3] until the period of the cretaceous formations, when the entire type of the ancient and long continued genus Ammonite was about to become extinct.
Turrilite.
The last genus I shall mention, allied to the family of Ammonites, is composed of spiral shells, of another form, coiled
- ↑ The Hamites grandis, (Sowerby, M. C. 593,) from the Greensand at Hythe, is of these large dimensions.
- ↑ The inner extremity of the Scaphite is coiled up like that of an Ammonite, (Pl. 44, Fig. 15, c. and 16) in whorls embracing one another; the last and outer chamber (a) is larger than all the rest together, and is sometimes (probably in the adult state) folded back so as to touch the spire, and thereby materially to contract the mouth, which is narrower than the last or outer chamber. (Pl. 44, Fig. 15, b.) in this character of the external chamber, the Scaphite differs from the Ammonite; in all other respects it essentially agrees with it; its transverse plates being numerous, and pierced by a marginal Siphuncle, at the back of the shell (Fig. 16, a.); and their edges being lobated, deeply cut, and foliated. (Fig. 15, c.)
- ↑ The Scaphites bifurcates occurs in the Lian of Wurtemburg, and Hamites annulatus in the Inferior oolite of France.
