134 



HOLOCENE DEPOSITS NEAR REIGATE. 



By LIONEL E. ADAMS, B.A. 



(Read before the Society, May 8th, 1907). 



The Rev. R. Ashington BuUen in an interesting paper, entitled 

 " Holocene Land Shells from Reigate,"^ has given a list of species 

 which he obtained from the face of a Holocene Deposit at the 

 Colley Chalk Pit (also known as the Horseshoe Pit) on the south 

 side of the downs near Reigate. In January, 1900, Mr. BuUen and 

 I visited the spot, and since then I have made frequent excursions 

 there to collect the shells that are found embedded in the continu- 

 ally weathering face. When Mr. BuUen first discovered the spot, 

 the deposit was much richer in species than it is to-day, probably 

 because it then extended to a lower level of the slope, where the 

 prehistoric shells were washed down the hill into a sort of " pocket." 

 I have recently come upon three more of these Holocene faces in 

 chalk pits along the same slope of the downs, all within a distance of 

 three miles. In none of these are the species very numerous, though 

 frequently the individuals of a few species are exceedingly plentiful. 

 These faces, which are clearly distinct from the underlying chalk, 

 vary from two to eight feet in depth, and are formed of chalk rubble 

 (mixed with upper greensand in the Horseshoe Pit) and flint flakes, 

 with a top layer of about nine inches of earth on which grass grows. 

 A comparison of the species contained herein with those now to be 

 found living on the surface is very interesting, as it shows how much 

 richer the local molluscan fauna was in bygone times, while the occur- 

 rence of Helix arbustorum, Liniax maxinms, Hyalinia ptira, Azeca 

 tridens, Helix hortensis and Bulimus monlanus,SL\l of which seem to have 

 died out, points to a damper habitat than now exists, with a certain 

 amount of wooded vegetation and a considerable mossy undergrowth. 

 The presence of Helix caperata, H itala, and Poviatias reflexus, how- 

 ever, reminds us that large stretches of open grass-land existed much as 

 is the case at the present day. H. pomatia and P. reflexus, which still 

 thrive along the whole range of these downs, are found at all depths 

 of the deposit. H. itala, though very abundant throughout, is rarely 

 if ever found now in a living state, and the cause of its disappear- 

 ance is very puzzling. 



A fourth section, which occurs within one hundred yards of the 

 Horseshoe, is similar in character, and gives similar results, there- 

 fore I have not devoted a separate column to it. It will be noticed 

 that I have not been able to add to Mr. BuUen's list. 



I Proc. Mai. Soc, vol. iii. , part 6, Oct. 1899. 



