ROOM IV. STATE OF PRESERVATION OF ENALIOSAURIANS.

369 contain a greater number, and more perfect skeletons of saurians, than others. The uppermost beds consist of Alum shale, with a profusion of ammonites and crinoidal remains. The next subdivision comprises strata of marlstone and blue marl, in which bones of Enaliosaurians are but rarely met with; but ammonites, belemnites, and other cephalopoda, and the usual marine shells and zoophytes of the Liassic formation are abundant.

The next group, the limestones, is the grand depositary of the reptilian remains,-" the inestimable treasury of the most splendid epoch in the physical records of our planet." Some of the thin intermediate layers of stone are, however, literally a mass of pentacrinites, and others are wholly made up of ammonites; the organic remains being more or less mineralized by pyrites.2

The most beautiful and perfect examples of Plesiosauri and Ichthyosauri collected by Mr. Hawkins, were extracted from these strata. The total thickness of the limestones, and alternating layers of marl, at Kingston, near Street, is about twenty feet; at Lyme Regis (forty miles from Street), the section east of Church Cliff, is thirty feet thick.

A bituminous marl, of a black colour, the last deposit in the series, contains similar remains with the limestones; and in addition, some fossil terrestrial vegetables not observed in the other strata.3

At the base of the Lias, and separating the lowermost shale from the uppermost Triassic bed beneath, there is a layer of coarse detritus, a few inches thick, commonly known as the Bone-bed, composed of mud and sand, and the debris of fishes and reptiles.*

STATE OF PRESERVATION OF ENALIOSAURIANS.-The remarkably perfect state of the skeletons of the Plesiosauri has already been pointed out; many of those of the Ichthyosauri are equally entire. In several of the specimens in the Museum, the bones are seen in all their integrity, as in recent anatomi