On the Wealden Beds of Brora, Sutherlandshire, with Remarks on the Relations of the Wealden Strata and Stonesfield Slate to the rest of the Jurassic System, and on the marine contemporary of the Wealden Series above the Portland Stone

Abstract

In the spring of 1843 I had the honour of transmitting to the Society a short account of two beds containing freshwater fossils, which were found by me, during the preceding summer, intercalated with the carboniferous portion of the Jurassic series of Brora. Having been prevented at the time of the discovery from making so detailed an examination of their relation to the rocks with which they were associated as was desirable, I again visited the locality, and now present the result of my observations on that occasion. My first object was to determine the exact age of the marine bed immediately above the main seam of coal, and with this view I collected as many of its fossils as circumstances permitted. These amount to twenty-five species of shells and some fragments of carbonized wood; but, with the exception of two Ammonites ( A. Kœnigi and A. sublœvis ), they are either enumerated in the lists published by Sir R.I. Murchison, are undescribed species, or are too imperfect for satisfactory determination. Eighteen of the shells are also found in different members of the Jurassic (oolitic) series of England, and of these the following occur in the unusually developed Kelloway Rock of Yorkshire:— Ammonites Gowerianus, Sow. Ammonites Kœnigi, Sow. Ammonites sublævis, Sow. Ostrea archetypa, Phil. Pecten lens, Sow. Modiola cuneata, Sow. Trigonia clavellata, Sow. Goniomya literata, Sow. The Ammonites Kœnigi and A. sublœvis are also associated in the equivalent strata at Kelloways Bridge, Wilts., and, as well as the A. Gowerianus , in the contiguous Oxford clay of Chippenham.