Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/685

 In two other diggings, instead of the loose shingle, occurs a clayey sand, mixed with small pebbles and numerous shells (Cerithium &c), out of twelve species of which, seven have not yet been found on the present beach. Most of the shells are broken and worn, owing no doubt to their having been rolled in shallow water with the sand and small shingle in which they are imbedded.

Further south, after digging in a bed representing that last described for about eighteen inches, the influx of spring water prevented the examination being carried further. Above it was a hard limestone without fossils, and above this a band of pale slate- coloured sand from 9 to 18 inches thick, equivalent to the pebbly clayey sand above mentioned. It is mixed with grit and small pebbles, and contains numerous specimens of the straight Cerithium which occurs in the equivalent bed; but all the shells found in it are broken and waterworn. Near the Creek there is a bluish sand ; and the shells in it are more perfect than in the beds previously mentioned. I had no opportunity of obtaining a measurement of its greatest thickness. From this particular band I have collected forty species of shells, of which there are eighteen that have no living representatives on the present sea-beach. I imagine that their descendants will have to be looked for further to the eastward along the coast.

There are two strata in the southern part of the section whose equivalents I have not been able to trace further north. One is a bright yellow sand, from 1 to 2 feet thick, containing numerous perfect specimens of Loripes edentula (Chenu) and Mactra, with both valves complete. The other is a pale slate-coloured sand, slightly clayey, varying from 2 to 5 feet in thickness, and containing numerous beautifully perfect shells. From the immense numbers of the Akceroe found in it, I have termed it the Akera-stratum. This deposit is in some places worn away, and divided in detached portions, as represented at a, a, a in Section T. It is at many places capped with a layer of waterworn fragments of shell-limestone, pieces of shell-grit containing small pebbles, and also waterworn shells of the present ocean. These last were, of course, left in the position in which they are found during the retreat of the sea to its present level. The number of species of shells that I have already obtained from this stratum is 71 ; of these, 27 have not been found on the present coast, and of 10 others it is doubtful whether they are still living in the neighbouring bay. The straight Cerithium, the Pectunculus, and others have sometimes been picked up by shell-collectors on the beach, mixed with recent shells ; but, possessing none of the fresh appearance of more recent shells, they have always borne evidence of having been disinterred.

§ 3. Pliocene or Postpliocene Strata (Raised Beaches) on the Coast and Inland. — The next deposits, so far as at present known, in succession to these, are shell-banks that are not only found along the coast, forming a raised sea-beach, as on the south side of the Zwartkops River's mouth, but also extending inland as raised banks nearly as far as Cradocktown. They are evidently far more extensive than those we have just been considering. The principal parts