MR. PRESTWICH's REPLY. 



113 



that the whorls are contiguous and more or less embracing, the chambers 

 numerous, and the siphuncle dorsal, or on the outer edge. The mouth 

 is usually more or less bordered or lobed, and in some cases constricted 

 at a longer or shorter distance below its margin. Several hundred forms 

 have been figured as species, but some reduction of the number will most 

 likely take place as we become more and more acquainted with the varia- 

 tions of form at successive periods of growth, the aberrations of specific 

 characters from local influences, and not unlikely the even possible 

 differences of the sexes. 



The first English work in which the A.mmonites communis was 

 described and figured is, we believe, Sowerby's " Mineral Conchology," 

 in which a variety is also figured under the title of Ammonites 

 angulatus. 



The beautiful fossil we have figured is a perfect specimen of the 

 species, possessing, without the slightest damage, the constricted and 

 bordered mouth of the adult individual. S. J. M. 



MR. PRESTWICH'S REPLY 

 TO THE LETTER OF THE REV. C. KINGSLEY 

 ON THE " HAGGERSTONE." 



To ike Editor of The Geologist. 



London, 22n(i February, 1858. 



Sib, — I quite agree with the Rev. Mr. Kingsley tbat the Hagger- 

 fitone of the Isle of Purbeck is not a transported boulder, but merely a 

 remnant in situ of some partially-removed Bagshot strata. I also think 

 it probable that a great part of the Bagshot series of Hampshire and 

 Dorsetshire is derived from the wear and destruction of a land of the 

 older and crystalline rocks — such rocks as now form the surface of Corn- 

 wall and Brittany ; and as the strata show greater fineness of material 

 at White Cliff Bay than at Alum Bay, in the Isle of Wight, and as again 

 they are still coarser around Poole Harbour, where they often pass into 

 grits, it is probable that much of the material of which they are 

 formed was drifted from a land nearer to the Poole area than to the 

 Hampshire area. On prolonging a line from the latter to the former, 

 it will point in a direction west and south - west ; i.e., towards 

 an old land, of which Cornwall and Brittany remain as the non- 

 submerged portion. The evidence afforded by the organic remains 

 points to the same conclusion, for the plant remains are more numerous, 

 and on the whole better preserved as we proceed from east to west, 

 being few and indistinct at White Cliff Bay ; more numerous as well 

 as more distinct at Alum Bay ; and still more plentiful at Bournemouth 

 and around Poole harbour — the leaves having become necessarily more 

 and more decayed as they were drifted away from the land in which they 

 grew. At the same time, shell remains are very scarce around Poole, 

 and are altogether absent at Alum Bay ; but they appear in some abun- 

 dance at White Cliff Bay, and are most numerous at Bracklesham 

 Bay, where, farther out in the old sea, marine life flourished under 



M 



