The families of Dinosauria, crocodiles, and Pterosauria or winged reptiles, are also represented in the Lias.

Sudden Destruction of Saurians.—It has been remarked, and truly, that many of the fish and saurians, found fossil in the Lias, must have met with sudden death and immediate burial; and that the destructive operation, whatever may have been its nature, was often repeated.

“Sometimes,” says Dr. Buckland, “scarcely a single bone or scale has been removed from the place it occupied during life; which could not have happened had the uncovered bodies of these saurians been left, even for a few hours, exposed to putrefaction, and to the attacks of fishes and other smaller animals at the bottom of the sea.”[[8]] Not only are the skeletons of the Ichthyosaurs entire, but sometimes the contents of their stomachs still remain between their ribs, as before remarked, so that we can discover the particular species of fish on which they lived, and the form of their excrements. Not unfrequently there are layers of these coprolites, at different depths in the Lias, at a distance from any entire skeletons of the marine lizards from which they were derived; “as if,” says Sir H. De la Beche, “the muddy bottom of the sea received small sudden accessions of matter from time to time, covering up the coprolites and other exuviæ which had accumulated during the intervals.”[[9]] It is further stated that, at Lyme Regis, those surfaces only of the coprolites which lay uppermost at the bottom of the sea have suffered partial decay, from the action of water before they were covered and protected by the muddy sediment that has afterwards permanently enveloped them.

Numerous specimens of the Calamary or pen-and-ink fish, (Geoteuthis bollensis) have also been met with in the Lias at Lyme, with the ink-bags still distended, containing the ink in a dried state, chiefly composed of carbon, and but slightly impregnated with carbonate of lime. These Cephalopoda, therefore, must, like the saurians, have been soon buried in sediment; for, if long exposed after death, the membrane containing the ink would have decayed.[[10]]

As we know that river-fish are sometimes stifled, even in their own element, by muddy water during floods, it cannot be doubted that the periodical discharge of large bodies of turbid fresh water in the sea may be still more fatal to marine tribes. In the “Principles of Geology” I have shown that large quantities of mud and drowned animals have been swept down into the sea by rivers during earthquakes, as in Java in 1699; and that indescribable multitudes of dead fishes have been seen floating on the sea after a discharge of noxious vapours during similar convulsions. But in the intervals between such catastrophes, strata may have accumulated slowly in the sea of the Lias, some being formed chiefly of one description of shell, such as ammonites, others of gryphites.

Fresh-water Deposits.—Insect-beds.—From the above remarks the reader will infer that the Lias is for the most part a marine deposit. Some members, however, of the series have an estuarine character, and must have been formed within the influence of rivers. At the base of the Upper and Lower Lias respectively, insect-beds appear to be almost everywhere present throughout the Midland and South-western districts of England. These beds are crowded with the remains of insects, small fish, and crustaceans, with occasional marine shells. One band in Gloucestershire, rarely exceeding a foot in thickness, has been named the “insect limestone.” It passes upward, says the Reverend P. B. Brodie,[[11]] into a shale containing Cypris and Estheria, and is full of the wing-cases of several genera of Coleoptera, with some nearly entire beetles, of which the eyes are preserved. The nervures of the wings of neuropterous insects (Figure 382) are beautifully perfect in this bed. Ferns, with Cycads and leaves of monocotyledonous plants, and some apparently brackish and fresh-water shells, accompany the insects in several places, while in others marine shells predominate, the fossils varying apparently as we examine the bed nearer or farther from the ancient land, or the source whence the fresh water was derived. After studying 300 specimens of these insects from the Lias, Mr. Westwood declares that they comprise both wood-eating and herb-devouring beetles, of the Linnean genera Elater, Carabus, etc., besides grasshoppers (Gryllus), and detached wings of dragon-flies and may-flies, or insects referable to the Linnean genera Libellula, Ephemera, Hemerobius, and Panorpa, in all belonging to no less than twenty-four families. The size of the species is usually small, and such as taken alone would imply a temperate climate; but many of the associated organic remains of other classes must lead to a different conclusion.

Fossil Plants.—Among the vegetable remains of the Lias, several species of Zamia have been found at Lyme Regis, and the remains of coniferous plants at Whitby. M. Ad. Brongniart enumerates forty-seven liassic acrogens, most of them ferns; and fifty gymnosperms, of which thirty-nine are cycads, and eleven conifers. Among the cycads the predominance of Zamites, and among the ferns the numerous genera with leaves having reticulated veins (as in [Fig. 349]), are mentioned as botanical characteristics of this era.[[12]] The absence as yet from the Lias and Oolite of all signs of dicotyledonous angiosperms is worthy of notice. The leaves of such plants are frequent in tertiary strata, and occur in the Cretaceous, though less plentifully (see [p. 303]). The angiosperms seem, therefore, to have been at the least comparatively rare in these older secondary periods, when more space was occupied by the Cycads and Conifers.

Origin of the Oolite and Lias.—The entire group of Oolite and Lias consists of repeated alternations of clay, sandstone, and limestone, following each other in the same order. Thus the clays of the Lias are followed by the sands now considered (see [p. 353]) as belonging to the same formation, though formerly referred to the Inferior Oolite, and these sands again by the shelly and coralline limestone called the Great or Bath Oolite. So, in the Middle Oolite, the Oxford Clay is followed by calcareous grit and coral rag; lastly, in the Upper Oolite, the Kimmeridge Clay is followed by the Portland Sand and limestone (see [Fig. 298]).[[13]] The clay beds, however, as Sir H. de la Beche remarks, can be followed over larger areas than the sand or sandstones.[[14]] It should also be remembered that while the Oolite system becomes arenaceous and resembles a coal-field in Yorkshire, it assumes in the Alps an almost purely calcareous form, the sands and clays being omitted; and even in the intervening tracts it is more complicated and variable than appears in ordinary descriptions. Nevertheless, some of the clays and intervening limestones do retain, in reality, a pretty uniform character for distances of from 400 to 600 miles from east to west and north to south.