Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/667

 Above the Modeler Drift {Ford). — The country for a distance of some 10 miles in a straight line between McLoughlin's and Modder Drift, on the Sundays River, I have not been able to examine ; but from the Modder Drift, for several miles, to the krantzes (precipices) below the Addo Drift, at Tunbridge's, three distinct fossiliferous bands make their appearance at intervals — that is to say, wherever the rocks are sufficiently exposed on the slopes of the hills that bound the S.W. side of the river.

Unfortunately, it is here the same as lower down the river, and the hill-sides are too much covered with debris and brushwood to enable any one to make a very accurate survey of the intervening strata. The belts vary from 2 to upwards of 3 feet in thickness. The lowermost, No 3 (see Section G, fig. 3), contains large numbers of Trigonia Herzogii, young and adult) ; but Trigonia conocardiformis is more abundant, and appears to be the characteristic shell here. Trigonia vau is often found, but it is far scarcer than those just mentioned ; also Cyprina rugulosa, Astarte Herzogii, and Ostrea.

The middle band, No. 2, Section G, is composed of a fossiliferous rock that appears to be, as before alluded to, the equivalent of the " Modiola- and Hamites-zone" at McLoughlin's. At present, however, I am not aware that any fragments of Hamites africanus have yet been found in this locality. Only in this bed, and in Nos. 6 & 7, at McLoughlin's, is Modiola Bainii found, as far as I have been able to learn ; and the accompanying shells, much like those found in the corresponding zone shown as No. 7, Section E, are Ammonites subanceps, Gastrochoena dominicalis (in fossil wood), Alaria coronata ?, Cardita nuculoides ?, Astarte Pinchiniana ?, and small specimens of Astarte, Cyprina ?, Psammobia ?, Ostrea.

The differences are that, above the Modder Drift, this stratum, No. 2, is much thicker than No. 7 at McLoughlin's Bluff, as it here attains, in some parts, a thickness of 3 feet ; the rock also is of a closer and harder texture, and of a more uniform grey colour, whilst the black specks of carbonized matter which characterize the " Hamites-zone " at McLoughlin's are, as far as I could observe, entirely wanting, owing most probably to the sediment of which this rock is composed having been deposited in deeper water* This stratum makes its appearance, as I have said, at intervals, wherever the mountain-side is sufficiently denuded of the super-incumbent soil : thus it is exposed a little above Modder Drift, again in a kloof (gully) called by Drs. Rubidge & Atherstone, from the number of Ammonites they found there, " Ammonite Kloof," and again some six miles above the Addo Drift, and beyond Commando Kraal on the Sundays River. These indications therefore enable us to trace this " Modiola-zone " from the bluff, in Section E, to the last-named spot, a distance of upwards of fifteen or sixteen miles. Other indications of this same bed may most probably be found between these different and widely separated points ; but the difficulties of making a thorough examination, as I have previously explained, are very great, covered as many of the hills are with dense entangled brushwood, while at the same time there