ORYCTOLOGY. 
tliis island : some very fine specimens have 
been found at Lime in Dorsetshire, in dif- 
ferent parts of Wiltshire, and at Whitby in 
Yorkshire. Tlie finest specimens are per- 
haps found in the neighbourhood of Bath, 
and in the Isle of Sheppey in Kent, at 
vphich latter place they are found exceed- 
ingly large, and still retaining a resplen- 
dent peaily shell. (Plate II. fig. 3.) 
The Cornu Amraonis, which, if we ex- 
cept the extremely minute shells of this kind 
which have been seen by Plancus, and 
others, in the sea sand on the Venetian 
sliores, may be said to be only known to us 
in a fossil state. 
Like the Nautilus, the Cornu Ammonis is 
divided into compartments, by regularly 
disposed partitions, and these partitions are 
perforated, as are those of the Nautilus, 
although it is by no means easy to point this 
out, except in very few specimens. 
There are none of the fossil shells, except 
perhaps the Anomiae, which can vie in the 
variety of their species with the Cornu Am- 
monis. The shell of some is perfectly 
smooth over its whole surface ; in others 
smooth at the sides, but ridged or beset 
with spines at the back ; and others, though 
smooth at the side, are crenulated at the 
back. The species most commonly met 
with have the shell variously ridged ; some 
with small close striae, and others with large 
and ronnd ridges. In some the ridges are 
single, in others bifurcated, and in others 
trifurcated. In some, and these are least 
common, the shell is tuberculated : these 
tuberculae differing considerably in differ- 
ent species, in their size, form, and dispo- 
sition. The different species proceeding 
from the intermixture of all these varieties, 
it must be obvious, must be exceedingly 
numerous : Scheuchzer was able to deter- 
mine the existence of one hundred and 
forty-nine species. The difference of size 
observable in these fossils is not less remark- 
able than tlie variety of their forms, some 
being found not much larger than the head ■ 
of a pin, whilst others have been found as 
large as the top of a small table. 
A peculiar appearance is observable on 
the surface of many of these fossils, which 
depends on the peculiar form of the septa 
which separate the chambers of the shell. 
These septa in the nautili are smooth, and 
terminate at the surface of the shell in a 
straight line ; but in the Cornua Ammonis 
they become undulated as they extend out- 
wardly ; and in some so much so /as to form, 
on the outer surface, deeply crenulated 
lines, giving the appearance of foliaceous 
sutures. When the cavities of the shell 
have become filled with stone, and the sep- 
ta just mentioned have been removed, as is 
frequently the case, by some chemical 
agent, the casts formed in the chambers , 
separate, each forming a curiously figured 
stone ; these separate casts have been term- 
ed spondylolites. (Plate II. fig. 4.) By the 
junction of these are formed the foliaceous 
sutures above mentioned. The Cornua 
Ammonia were formerly called serpent- 
stones ; the appearance which they yield of 
a serpent coiled having led the vulgar to 
consider them as petrified serpents. 
The fossil Cones are very few when com- 
pared with the numerous species known in 
a recent state ; the same may be also said 
of the Cyprmae. In both these genera the 
species are mostly made out more from the 
colour and the markings of the shells, than 
from the peculiarities of their form ; but in 
the fossil shells the colours no longer exist, 
and of course the species in these can very 
seldom be presumed. The fossil Volutes, 
as far as can be judged from their form 
alone, differ generally from the recent spe- 
cies. With respect to the genus Buccinum, 
Strombus, and Miirex, the number of spe- 
cies of the fossil shells do not appear to 
equal those which are known in a recent 
state. This is the case also, in a still greater 
degree, with the genus Trochus. The fossil 
shells of the genus Turbo are pretty numer- 
ous, and some of them very closely resem- 
ble those of known recent species. One 
fossil shell of this genus is very remarkable 
for its vast size, being upwards of a foot in 
length. The cast of another species is so 
large as to weigh four or five pounds. 
Nothing like this occurs with respect to the 
species of the genus Helix : the fossil shells 
of this genus very much resemble those 
which are recent, and are not found of any 
considerable magnitude. The fossil shells 
of the genus Nerita by no means display so 
• many species as the recent; but some of 
the fossil species far exceed the recent in 
size, and one in particular is twelve 
times the size of any known recent spe- 
cies. Of the genus Haliotis, it is not 
positively determined that a single shell 
has been seen, which could be considered 
as fossil. Fossil shells of the genus Patelta 
are by no means common. Several species 
have, however, been found in France, in a 
state of excellent preservation. Some few 
also have been found in the cliffs at Har- 
wich, and others, of a different species, 
