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 Ammonites 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 the Editor of The Geologist. 
London, 22nd February, 1858. 
Sir, — I quite agree with the Rev. Mr. Kingsley that the Hagger- 
stone 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 Clifi^ 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 aff'orded 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 ClilF Bay, and are most numerous at Bracklesham 
Bay, where, farther out in the old sea, marine life flourished under 
M 
