128 



THE GEOLOGIST. 



throws some doubt whether the flint-drift of our section may not 

 have been brought down by landslips such as are now common at 

 the Cape, and have been a portion of a former undercliff since cut 

 into by the action of the sea. No fragments of shells, sand, or rock, 

 indicating any amount of regeneration, are to be found in the " flint- 

 drift," which consists entirely of ferruginous sand and angular pieces 

 of flints, and which so far seems, allowing for local differences of 

 mineralogical character, to be identical with the flint-drift so exten- 

 sively distributed over this region. The next question to be deter- 

 mined, is how far back in geological history the species of shells 

 found in the subjacent sand can be found to date their existence, be- 

 cause certainly the age of this shell-sand has to be mainly determined 

 by its organisms, there being but little concurrent evidence as yet ob- 

 tained from other sources than the mollusca found in the sand. The 

 following are placed by Professor Forbes in his list of " species now 

 living in British seas and found fossil in true glacial beds :" — Mactra 

 solida, Tellina solidula, Cardium edule, JVucula tenuis, Littorina lit- 

 torea ; and Mactra stultorum is placed by the same author among 

 the British species not found fossil in typical glacial beds, but occur- 

 ring in contemporaneous Italian newer Pliocene strata. 



The evidence therefore of the shells brings the age of this Havre 

 sand between two limits, that of the Pleistocene on the one hand, 

 and the Kecent or Actual period on the other. The flint-drift, being 

 superincumbent, must consequently take its place at a more recent 

 stage than the sand within the same interval, if it be truly in situ. 



The fossils of the recent shell-sand are well preserved, although 

 extremely brittle, traces of colour being frequent, and the specimens 

 of periwinkles, though not numerous, are hard, and but little changed 

 in structure, excepting by the loss of albuminous matter. The por- 

 tion of a tooth of Eleplias primigenius, found on the shore in a mass 

 of hardened sandy material near the termination of the valley of St. 

 Addresse, and preserved in the cabinet of M. Mambard, indicates the 

 existence and proximity of some Pleistocene deposit, the discovery 

 of which would possibly throw much light on the position in time 

 that our recent shell-sand ought to occupy. It would be highly in- 

 teresting to determine the occurrence, and trace the connection of a 

 freshwater marl or other deposit, containing bones of the Pleistocene 

 mammalia, in this neighbourhood. In the drift exposed in the Cape 

 cliff-section, there are evident signs of rude inclined stratification on 

 the sides of the hollows and shorter sand-pipes of the chalk, and 



