A Manual of Elementary Geology / or, The Ancient Changes of the Earth and its Inhabitants as Illustrated by Geological Monuments

by Sir Charles Lyell

Fig. 144. Fusus contrarius.

Fig. 145. Murex alveolatus.

Fig. 146. Nassa granulata.

Fig. 147. Cypræa coccinelloides.

Fig. 144. half nat. size; the others nat. size.

Among the bones and teeth of fishes are those of large sharks (Carcharias), and a gigantic skate of the extinct genus Myliobates, and many other forms, some common to our seas, and many foreign to them.

The distinctness of the fossils of the coralline crag arises in part from higher antiquity, and, in some degree, from a difference in the geographical conditions of the submarine bottom. The prolific growth of corals, echini, and a prodigious variety of testacea, implies a region of deeper and more tranquil water; whereas, the red crag may have formed afterwards on the same spot, when the water was shallower. In the mean time the climate may have become somewhat cooler, and some of the zoophytes which flourished in the first period may have disappeared, so that the fauna of the red crag acquired a character somewhat more nearly resembling that of our northern seas, as is implied by the large development of certain sections of the genera Fusus, Buccinum, Purpura, and Trochus, proper to higher latitudes, and which are wanting or feebly represented in the inferior crag.

Some of the corals of the lower crag of Suffolk belong to genera unknown in the living creation, and of a very peculiar structure; as, for example, that represented in the annexed [fig. (148.)], which is one of several species having a globular form. The great number and variety of these zoophytes probably indicate an equable climate, free from intense cold in winter. On the other hand, that the heat was never excessive is confirmed by the prevalence of northern forms among the testacea, such as the Glycimeris, Cyprina, and Astarte. Of the genus last mentioned (see [fig. 149.]) there are about fourteen species, many of them being rich in individuals; and there is an absence of genera peculiar to hot climates, such as Conus, Oliva, Mitra, Fasciolaria, Crassatella, and others. The cowries (Cypræa, [fig. 147.]), also, are small, and belong to a section (Trivia) now inhabiting the colder regions. A large volute, called Voluta Lamberti ([fig. 150.]), may seem an exception; but it differs in form from the volutes of the torrid zone, and may, like the living Voluta Magellanica, have been fitted for an extra-tropical climate.

Fig. 148.