Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/665

 being made. The existence of this Astarte- and Trigonia-band seems to point out that the position I have given to the sections (on the Zwartkops) is the most probable one.

The fossiliferons strata Nos. 6 & 7, in Section E (fig. 3), were evidently deposited under very different circumstances from any of the others ; and wherever the one I have styled the Modiola- and Hamites-zone (No. 7) makes its appearance, it possesses the same lithological character. I have given this name to it on account of the numerous specimens of Modiola Bainii and fragments of the Hamites africanus found in it. In this locality (McLoughlin's Bluff) this stratum is full of small fragments of carbonized wood, which rub down to black powder under the finger. These minute fragments seem to indicate that the sedimentary matter of which this particular portion of the bed is composed, must have been the deposit of some current of water laden with innumerable small pieces of vegetable drift, such as we see washed up in the present day on the seashore, after rains, near the mouths of small rivers.

Some miles further up Sundays River, where this bed is again exposed, and where its thickness is much greater, these specks of carbonized matter are wanting — an indication that this latter portion was most probably deposited further off shore, or from a different direction; but I shall have again to allude to this in my observations on the Upper Sundays River. The shells also of this stratum are, with few exceptions, of a very different character from those of the Astarte- and Trigonia-beds, the shells of the latter being, for the most part, strong massive shells, fit to live along the coasts of an open sea, whilst those found in the zones of which I am now speaking are, most of them, thin and fragile. The rock itself is of a much looser texture than the associated non-fossiliferous sandstones — while these latter, which intervene between this bed and the uppermost layer, increase in friability as they ascend, and show a considerable difference from the compact sandstones of the Lower Zwartkops. The rock composing the Hamites-zone is patchy in colour, appearing in some places of a reddish sandy tint, but more frequently grey. This was the bed (No. 7) in which the large, coiled, broken fossil, thought to have been an Ancyloceras (?), was discovered by Major (now Lieut.-Col.) Rocke. In no other, that I am aware of, have Hamites africanus and Belemnites africanus been found : fragments of the former are here exceedingly abundant ; but the latter is rare. Modiola Bainii seems almost exclusively confined to this stratum. Fragments of either Hamites or Modiola, found in the debris of the neighbouring cliffs, are always a sure indication of the close proximity of this band. The principal shells characteristic of this zone, are : — Hamites africanus (very numerous), Ancyloceras (?) (two specimens), Trigonia Goldfussi, Tr. conocardiformis (young), Crassatella complicata, Modiola Bainii (numerous), Mytilus Stowianus, Mytilus Rubidgei, Belemnites africanus (rather scarce) ; also, I believe, Alaria coronata, and small specimens of Astarte, Cyprina (?), Psammobia (?), and Ostrea (narrow, curved).