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

by Sir Charles Lyell

White chalk.

A branching sponge in a flint, from the white chalk. From the collection of Mr. Bowerbank.

With these mollusca are many corals ([figs. 209], [210], [211.]) and sea urchins ([fig. 212.]), which are alike marine, and, for the most part, indicative of a deep sea. They are dispersed indifferently through the soft chalk, and hard flint, and some of the flinty nodules owe their irregular forms to inclosed zoophytes, as in the specimen represented in [fig. 211.], where the hollows in the exterior are caused by the branches of a sponge seen on breaking open the flint, [fig. 210.]

Fig. 212.

Ananchytes ovata. White chalk, upper and lower.

• a. Side view.
• b. Bottom of the shell on which both the oral and anal apertures are placed; the anal being more round, and at the smaller end.