Charles Lyell

“ Other genera contain some fresh-water and some marine species, as Cottus, Mugil, and Anguilla, or eel. The rest are either common to rivers and the sea, as the salmon; or are exclusively characteristic of salt-water. The above observations respecting fossil fishes are applicable only to the more modern or tertiary deposits; for in the more ancient rocks the forms depart so widely from those of existing fishes, that it is very difficult, at least in the present state of science, to derive any positive information from ichthyolites respecting the element in which strata were deposited. ”

“ Some limestones consist almost exclusively of corals, and in many cases it is evident that the present position of each fossil zoophyte has been determined by the manner in which it grew originally. The axis of the coral, for example, if its natural growth is erect, still remains at right angles to the plane of stratification. If the stratum be now horizontal, the round spherical heads of certain species continue uppermost, and their points of attachment are directed downward. This arrangement is sometimes repeated throughout a great succession of strata. ”

“ It is not uncommon to meet with layers of vegetable matter, impressions of leaves, and branches of trees, in strata containing fresh-water shells; and we also find occasionally the teeth and bones of land quadrupeds, of species now unknown. The manner in which such remains are occasionally carried by rivers into lakes, especially during floods, has been fully treated of in the "Principles of Geology." ”

“ We should often be unable to detect any signs of stratification or of successive deposition, if particular kinds of fossils did not occur here and there at certain depths in the mass. At one level, for example, univalve shells of some one or more species predominate; at another, bivalve shells; and at a third, corals; while in some formations we find layers of vegetable matter, commonly derived from land plants, separating strata. ”

“ During these ages, the water must have been clear and transparent, for such corals can not live in turbid water.
In like manner, when we see thousands of full-grown shells dispersed everywhere throughout a long series of strata, we can not doubt that time was required for the multiplication of successive generations; and the evidence of slow accumulation is rendered more striking from the proofs, so often discovered, of fossil bodies having lain for a time on the floor of the ocean after death before they were imbedded in sediment. ”

“ Nothing, for example, is more common than to see fossil oysters in clay, with Serpulae, or barnacles (acorn-shells) , or corals, and other creatures, attached to the inside of the valves, so that the mollusk was certainly not buried in argillaceous mud the moment it died. There must have been an interval during which it was still surrounded with clear water, when the creatures whose remains now adhere to it grew from an embryonic to a mature state. ”

“ Now the series of events here attested by a single fossil may be carried a step farther. Thus, for example, we often meet with a sea-urchin (Ananchytes) in the chalk (see Figure 12) which has fixed to it the lower valve of a Crania, a genus of bivalve mollusca. The upper valve (b, Figure 12) is almost invariably wanting, though occasionally found in a perfect state of preservation in white chalk at some distance. In this case, we see clearly that the sea-urchin first lived from youth to age, then died and lost its spines, which were carried away. ”

“ It is clear much time must have been required for the accumulation of strata to which countless generations of Diatomaceae have contributed their remains; and these discoveries lead us naturally to suspect that other deposits, of which the materials have been supposed to be inorganic, may in reality be composed chiefly of microscopic organic bodies. ”

“ Although fresh-water formations are often of great thickness, yet they are usually very limited in area when compared to marine deposits, just as lakes and estuaries are of small dimensions in comparison with seas. ”

“ From what we know of the growth of similar zoophytes in modern reefs, we infer that the rate of increase was extremely slow, and some of the fossils must have flourished for ages like forest-trees, before they attained so large a size. ”

“ Limestones formed of Corals and Shells. Proofs of gradual Increase of Strata derived from Fossils. Serpula attached to Spatangus. Wood bored by Teredina. Tripoli formed of Infusoria. Chalk derived principally from Organic Bodies. Distinction of Fresh-water from Marine Formations. Genera of Fresh-water and Land Shells. Rules for recognising Marine Testacea. Gyrogonite and Chara. Fresh-water Fishes. Alternation of Marine and Fresh-water Deposits. ”