This character of the skin, and the serrated crest, are accurately given in the restoration, the major part of which, however, is necessarily at present conjectural, and carried out according to the general analogies of the saurian form. The size is indicated with more certainty according to the proportions of the known vertebræ and other bones.
No. 6. Diagram of the Slab containing the Bones of Hylæosaurus.
THE OOLITE.
The division of the secondary formations, called “Oolite,” takes its name from the most characteristic of its constituents, which is a variety of limestone composed of numerous small grains, resembling the “roe” or eggs of a fish, whence the term, (from the Greek oon, an egg, lithos, a stone). The oolite, however, includes a great series of beds of marine origin, which, with an average breadth of thirty miles, extend across England, from Yorkshire in the north-east to Dorsetshire in the south-west.
The oolite series lies below the Wealden, and where this is wanting, below the chalk, and consists of the following subdivisions, succeeding each other in the descending order:—
Oolite.
| Upper. | - | Portland stone and sand. | |
| Kimmeridge clay. | |||
| Middle. | - | Coral rag. | |
| Oxford clay. | |||
| Lower. | - | Cornbrash and forest marble. | |
| Great oolite and Stonesfield slate. | |||
| Fuller’s earth. | |||
| Inferior oolite. | |||
Upon the portion of the island representing the oolite series, the most conspicuous of the restored animals of that period is—