Mr. Austen on the Geology of the South-east of Surrey. 67 



drifted over the bed where we now find them. This species however 

 is not confined to such layers, but is found in extraordinary numbers 

 in each separate bed ; and in another instance an Astrcea had time 

 to spread itself out over the surface. 



Considering the small number of animal remains we yet possess 

 from the chalk formation, when viewed with reference to its vast 

 thickness, there being not more than four or five species to 100 feet, 

 it seems hazardous to refer the whole of this wide-spread mass of cal- 

 careous matter to the destruction of animal structures ; but the im- 

 pression constantly produced by a microscopic examination of the 

 white chalk in every place has been, that it was the deep sea deposit 

 of a wide ocean, which in parts teemed with animal life, but of which 

 the localities have long since disappeared in the extensive destruction 

 which it has everywhere experienced ; and that all we have to judge 

 from is such portion as was not generally calculated to support animal 

 life, with the exception perhaps of Foraminifera and Brachiopods : 

 the specific gravity of shells and corals is in favour of the wide dis- 

 tribution of their materials when pounded. 



Nor is this purely hypothetical : there are some remarkable beds 

 a little below that portion of the deposit last described which bear 

 it out : they are beds which were apparently deposited when the 

 waters could drift rather coarser materials than usual ; so that the 

 greatest portion consists of broken branches of corals, shells and 

 Echinoderms, cemented by the usual comminuted matter of the or- 

 dinary chalk strata, Eschara cancellata, E. pyriformis, Cellepora bi- 

 punctata, Ceriopora madreporacea, Retepora truncata, Serpula plexus, 

 and Cidaris vesiculosa are the principal species met with. 



For a very considerable depth below this, through that portion 

 where the seams of flint are most regular, it is almost in vain to 

 search for any traces of animal life. This condition of things is con- 

 tinued downwards as far as the chalk without flints, where Inocera- 

 mus mytiloides and Cuvieri,Lima Hoperi, Plagiostomce&ndTerebratula, 

 become abundant, together with the remains of fishes ; and which 

 beds are succeeded by others which afford a gray limestone, and con- 

 tain Ammonites rhotomagensis, A. Mantelli, A. lewesiensis, A, varians, 

 Turrilites tuberculatus, Scaphites tequalis, Pecten Beaveri, and Anan- 

 chytes radiatus. 



This lower chalk, which through a considerable thickness had 

 been gradually becoming more compact, thick-bedded and dark-co- 

 loured, suddenly changes to a rock, exactly resembling the upper 

 white fragmentary beds. This portion of the series, taken in a de- 

 scending order, slowly acquires an admixture of sand and green 

 earth, so as to become first a craie chloritee, till by the further di- 

 minution of the calcareous matter we reach the bright green beds of 

 the upper greensand with Plicatula inflata : below these strata of 

 white, blue, calcareous matter again occur, containing Ammonites 

 rhotomagensis and Mantelli, offering a striking contrast to the beds 

 above them and the rock gault immediately below : through this 

 portion again traces of animal life are hardly to be found. 



The gault clay contains Ammonites splendens, A. interruptus, A* 



F2 



