ORYCTOLOGY. 
since, though materially different, they ap- 
proach very nearly in their general form to 
the reeent species. Those which possess a 
hemispherical, or a nearly orbicular form, 
with large mamilla-like protuberances, and 
the anus disposed vertically, have been dis- 
tinguished as tlie turban echini {echini ci- 
dares ) ; those, which resemble a shield or 
buckler in tbeir figure are termed the shield 
echini (clypei Kleinii) ; and one of the lar- 
gest of these has been named the polar 
stone by Dr. Plot(Plot’s Oxfordshire, p, 91.) 
When of .a depressed circular form, with 
the anus in the edge of tlie, inferior part, 
they are the fibula; of Klein ; of a conical 
form, the eaglestone of the Germans {co- 
nuli, Kleinii)-, with a circular base, the 
quoit echinus (discoidei, Kleinii). When 
the base is an acute oval, the mouth and 
anus being at the opposite ends, they are 
termed the helmet echinis, {cassides et ga- 
lea, Kleinii) ; and when heart-shaped, with 
a sulcated superior surface, they are called 
snake’s hearts {spatangi, Kleinii.) 
The attempt to particularize the various 
species of fossil shells which have been found 
would require a large volume : all that can 
be here done is to notice some of those 
which totally differ from any which exist in 
a recent state, and to offer some few re- 
marks on those which approximate, or are 
perhaps similar to some of the species which 
are known in a recent state. 
With respect to the state in which fossil 
shells are found, it is necessary to remark, 
that, in some situations, shells which have 
been buried for ages, by the natural changes 
which the surface of the earth has under- 
gone, are found very little changed, ex- 
cept from the loss of colour, and having 
been rendered extremely fragile; that in 
other situations the substance of the shell 
has been so injured, as to be reduced to 
very small fragments, and even to a fine 
powder, leaving in some instances a stony, 
correctly moulded, cast of the cavity of 
the shell; that very frequently the sub- 
stance of the shell is entirely altered, hav- 
ing become a calcareous stone, or a silici- 
ous or pyritous mass, and that the shells of 
a former world are frequently found in 
masses of marble, which is called luma- 
chelli, or shelly marble. 
Of the Multivalves, the chiton does not 
appear to have been found in a mineralized 
state ; and although several species of Lepas 
have been found in a mineral state, they 
are by no means frequent fossils. Lepas 
anserifera is said to have been found fossil, 
as well as Lepas diadema; these must, how- 
ever, be exceedingly rare fossils. 
Fossil shells of the Pholas are by no means 
common; the Pholas crispata has been 
however, found among the Harwich fos- 
sils. 
Fossil bivalves are very common fossils ; 
they are, as might be expected, very sel- 
dom found in pairs, except when united by 
a lapideous mass, which prevents the exa- 
mination ol their hinge, or their internal 
structure, which in many fossil shells, are 
objects highly w'orthy of examination. 
The Mya pictorum is described by So- 
lander as existing among our Hampshire 
fossils ; a fossil mya of three or four inches 
in length, is found also in the rocks near 
Bognor. Remains of the solen siliqua, 
and of tlie solen ensis, have been found at 
Harwich, and a small fossil shell, named by 
Solander solen ficus, has been found be- 
tween Lymington and Christchurch. 
Fossil shells of the genus Tellina, as well 
as of cardium, mactra, donax, venus, spon- 
dylus, chama, area, and particularly ostrea, 
have been found of many species But no 
bivalve exists as a fossil in such prodigious 
numbers, and in such various species, as 
those of the genus Anomia. These shells 
are characterized by the beak of the larg- 
est or under valve, which is perforated, be- 
ing greatly produced, rising or curving over 
the beak of the smaller or upper valve. 
Anemia lacunosa (Plate II. fig. 1 .) is one of 
the most abundant of these species. They 
are found in considerable quantities in dif- 
ferent parts of England, particularly in 
Lincolnshire, Warwickshire, and Glouces- 
tershire. Anomia terebratula, (Plate II. 
fig. 2), is another fossil of this genus, which 
exists in different counties in this island, in 
great abundance. 
. Of the genus Mytilus several species are 
known as fossils, some of which approach 
very near to those which are known recent : 
one in particular appears to differ very lit- 
tle indeed from Mytilus modiolus. Fossil 
shells of the genus Pinna, in any tolerable 
state of preservation, are not frequently 
found : the shells are in general so fragile as 
to render it very difficult to obtain them 
tolerably perfect; or so that but little in- 
formation can- be yielded respecting the 
species to which they belong. 
No fossil shell appears yet to have been 
found which can with certainty be placed 
under the genus Argonauta. But of tlie ge- 
nus Nautilus, specimens are very frequent. 
These have been found in several parts of 
