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Published online by Cambridge University Press: 01 May 2009
2. Middle and Lower Cambrian.—Investigations in continental Europe were, meanwhile, preparing the way for a new chapter in the history of the Lower Palæozoic rocks. A series of sedimentary beds in Sweden and Norway had long been known to abound in singular petrifactions, some of which had been examined by Linnæus, who gave to them the name of Entomolithi. They were also studied and described by Wahlenberg and by Brongniart, the latter of whom, from two varieties of the Entomolithus paradoxus, Linn., established in 1822 two genera, Paradoxides and Agnostus.
Reprinted from the “Canadian Naturalist,” new series, vol. vi. no. 3, p. 294.
page 461 note 1 The Longmynd rocks in Shropshire are alone estimated at 20,000 feet; but their supposed equivalents, the Harlech rocks of Pembrokeshire, have a measured thickness of 3,300, while the Llanberris and Harlech rocks together, in North Wales, equal from 4,000 to 7,000 feet, and the Lingula-flags and Tremadoc slates, united, about 7,000 feet. The Bala group in the Berwyns exceeds 12,000 feet, and the proper Silurian, from the base of the Upper Llandovery or May Hill Sandstone, attains from 5,000 to 6,000 feet; so that the aggregate of 30,000 feet may be considered below the truth. [Mem. Geol. Survey; vol. iii. part 2, pp. 72, 222, and Siluria, 4th ed. p. 185.]