502 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



There cannot be the slightest doubt that, if future explorers will 

 . arrange the fossils they obtain from these different strata according 

 to the particular hand from which they are derived, the scanty 

 lists here given will be greatly enlarged. 



There is another somewhat remarkable feature in the shells of 

 this (No. 7) and the stratum (No. 6) immediately above it — namely, 

 that the large Trigonice are wanting, although there are numbers 

 of the smaller kind, and young individuals. Puture investigations 

 will perhaps modify these conclusions. The Hamites and Modiola, 

 from which I have named the zone, may be found to extend into 

 others in reduced numbers ; but in this particular zone they have a 

 great numerical superiority. 



In the bed marked 6, the same type of shells appears as in No. 7. 

 The rock is also apparently of the same kind. But only a few 

 small fragments of Hamites are found ; and in the bed above, 

 marked 5, the Hamites seems to have disappeared entirely, and 

 apparently all the peculiar shells that accompanied it — their places 

 being supplied by others of a different character. Amongst these the 

 principal is the beautiful Trigonia ventncosa. It abounds here, and 

 is, in fact, the characteristic fossil of the bed in this particular 

 locality. A few isolated specimens have been found in the Zwart- 

 kops strata ; but here they are, in some places, massed together in 

 thousands, outnumbering every other shell. Trigonia vau is also 

 very abundant ; and hence, in the general Section (fig. 3), I have 

 called this (No. 5) the Trigonia-ventncosa- and T.-vau-2,one. Pine 

 specimens of Gervillia dentata also have been obtained from it, toge- 

 ther with Exogyra imhricata, Fecten Subidgeanus, and Turbo 

 Stoiuianus. 



In bed No. 4 the Trigonice, compared with those in No. 5, are 

 not only very much fewer and smaller, but, from some alteration 

 of circumstances, ai^pareutly were disappearing from this part of 

 the ancient ocean. The remains of other shells are also far less 

 abundant than in the lower zones. The sandstone above No. 4 is 

 much altered in character compared with those underlying it, being, 

 as I have before remarked, less compact, and far more coarse and 

 friable than those below. This difference of texture increases the 

 nearer we approach the upper portion of the section, where the 

 sandstone seems to assimilate in lithological character more to the 

 upper sandstones of the Koega, and to those interlaminated ivith the 

 days at the Bethelsdorp Saltpan (see further on), than to any others. 



Immediately above these, as shown in Section E (fig. 3), is a shell- 

 bed, from 3 to 5 feet thick, composed of small fragments of shells, 

 thickly interspersed with a species of Ostrea. This stratum seems to 

 be of Pliocene or Postpliocene age, and to be the^equivalent of the 

 upper shell-limestone on the Zwartkops and the Koega. Above 

 this, again, is a conglomerate, varying from 3 to 6 feet in thickness. 

 This is capped with tufaceous limestone, from 2 to 3 feet thick ; and 

 above the limestone is a red, sandy, marly clay, varying, according 

 to the inequalities of the surface, from 4 to 6 feet. I send a sketch 

 of the bluff (fig. 2), the better to show the formation. 



