On the age of the Silurian Beds of the Pentland Hills

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Abstract
The object of this paper was to show that the Silurian beds situated near to the source of the North Esk, a quarter of a mile above the North Esk reservoir, and described by Mr D. J. Brown in his paper, read 21st February 1867 (see p. 23, Part I.), as of Ludlow and Wenlock age, are, probably, all synchronous with the Upper and Lower Ludlow of England. If the representatives of the Wenlock shales occur in this district, it is in the beds below the reservoir, which are about 400 fathoms lower than the beds described as Wenlock by Mr D. J. Brown. The reasons for coming to this conclusion are,— first, In the beds below the reservoir nothing but Wenlock fossils have been found; second, The number of cyclobranchiate shells in Mr Brown’s Wenlock strata bears a very large proportion to the other organisms, a proportion unknown in the Wenlock, though common in the Ludlow; third, In a bed immediately overlying the Wenlock of Mr Brown, and described by him as Lower Ludlow, Mr Salter found a portion of an Upper Silurian crustacean; and, fourthly, Because Mr Archibald Geikie, Mr Salter, Professor Young, and the other eminent geologists who have examined the district, are of opinion that the upper fossiliferous beds should be referred to the Upper Ludlow age; the beds immediately underlying them to the Lower Ludlow; and the fossiliferous beds, 400 fathoms below these, to the Wenlock.

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