We have every reason to conclude that the gaps which occur, both between the larger and smaller sections of the English Oolites, imply intervals of time, elsewhere represented by fossiliferous strata, although no deposit may have taken place in the British area. This conclusion is warranted by the partial extent of many of the minor and some of the larger divisions even in England. [1] Elements of Geology, 4th edition. [2] I allude to several Zeuglodons found in Alabama, and referred by some zoologists to three species. [3] See Phil. Trans. 1850, p. 363; also Huxley, Memoirs of Geol. Survey, 1864; Phillips, Palæont. Soc. [4] P. Scrope, Proc. Geol. Soc., March, 1831. [5] Proceedings Geol. Soc., vol. i, p. 414. [6] A figure of this recent _Myrmecobius_ will be found in my Principles of Geology, chap. ix. [7] Owen’s British Fossil Mammals, p. 62. CHAPTER XX. JURASSIC GROUP—_continued_—LIAS. Mineral Character of Lias. — Numerous successive Zones in the Lias, marked by distinct Fossils, without Unconformity in the Stratification, or Change in the Mineral Character of the Deposits. — Gryphite Limestone. — Shells of the Lias. — Fish of the Lias. — Reptiles of the Lias. — Ichthyosaur and Plesiosaur. — Marine Reptile of the Galapagos Islands. — Sudden Destruction and Burial of Fossil Animals in Lias. — Fluvio-marine Beds in Gloucestershire, and Insect Limestone. — Fossil Plants. — The origin of the Oolite and Lias, and of alternating Calcareous and Argillaceous Formations. Lias.—The English provincial name of Lias has been very generally adopted for a formation of argillaceous limestone, marl, and clay, which forms the base of the Oolite, and is classed by many geologists as part of that group. The peculiar aspect which is most characteristic of the Lias in England, France, and Germany, is an alternation of thin beds of blue or grey limestone, having a surface which becomes light-brown when weathered, these beds being separated by dark-coloured, narrow argillaceous partings, so that the quarries of this rock, at a distance, assume a striped and ribbon-like appearance. The Lias has been divided in England into three groups, the Upper, Middle, and Lower. The Upper Lias consists first of sands, which were formerly regarded as the base of the Oolite, but which, according to Dr. Wright, are by their fossils more properly referable to the Lias; secondly, of clay shale and thin beds of limestone. The Middle Lias, or marl-stone series, has been divided into three zones; and the Lower Lias, according to the labours of Quenstedt, Oppel, Strickland, Wright, and others, into seven zones, each marked by its own group of fossils. This Lower Lias averages from 600 to 900 feet in thickness. From Devon and Dorsetshire to Yorkshire all these divisions, observes Professor Ramsay, are constant; and from top to bottom we cannot assert that anywhere there is actual unconformity between any two subdivisions, whether of the larger or smaller kind.