Note 1078 — Chapter VII

In the older half of the secondary rocks, mammals are hardly to be found, and they do not become common until the tertiary. Murchison's Siluria, pp. 466, 467; and Strickland on Ornithology, p. 210 (Brit. Assoc. for 1844). So, too, in the vegetable kingdom, many of the plants in the tertiary strata belong to genera still existing; but this is rarely the case with the secondary strata; while in the primary strata, even the families are different to those now found on the earth. Balfour's Botany, pp. 592, 593. Compare Wilson's additions to Jussieu's Botany, 1849, p. 746; and for further illustration of this remarkable law of the relation between advancing time and diminished similarity, a law suggesting the most curious speculations, see Hitchcock's Geology, p. 21; Lyell's Geology, p. 183; and Owen's Lectures on the Invertebrata, 1855, pp. 38, 576.