CONCH 
fa a living ftate. For- not only tingle fpecies of foflil 
(hells yet remain undifcovered in their living ftate; but 
genera, and even whole families, (till exift in the feas, 
which are not yet known to us, other wife than in the foflil 
ftate. Foftil limpets are very rarefy met with ; however, 
there are two kinds, which deferve particular notice. 
The firll is a fmall fpecies called the fool’s cap. It feems 
different from the Weft Indian kind, but approaches it 
nearly. This is not unfrequently found in the calca¬ 
reous foils of France. The (econd is a very curious and 
remarkable (hell, and the fragments of it, called by fofiilo- 
gifts trichites, are found in great abundance in the Eng- 
lifli chalk-pits ; yet the (hells are fo rarely to be met with 
entire, that we have heard of only four, which were found 
in the cliffs near Dover. Thefe'limpets are very large, 
and nearly referable a fingle (hell of a bivalve. They 
feem to be of two kinds, and are more irregular than that 
(hell; and, inftead of being falcated lengthwife, they are 
circularly wrought, or in a tranfverfe manner, with very 
high irregular ridges, not thickly, but rather thinly, fet. 
Thefe (hells are very thick. One fort is high, or coped, 
the other is broad or flattifti. The infideis quite fmooth, 
the edges turn outwards, and, under the beak, or that 
part which anlwers to the hinge in bivalves, they ftretch 
out, towards, the fame fide, into a broad flat ledge, the 
perpendicular fide of which is curioufly worked w'ith 
ftraight and parallel furrows, like the hinge of a multar- 
iiculate bivalve. On the top or beak it has a large, wide, 
roundifli opening, which, from its remarkable thinnefs, 
makes it difficult to determine whether it be a natural 
perforation, or an accidental fra&ure ; though, by its re¬ 
gular edge, and being quite alike in all the four fpecimens, 
one would incline in favour of the former. Figures of 
the limpet are exhibited in the engraving. 
HALIOTIS, AURES MARIN-®, or SEA EARS. 
The effential clMra&er of this family is as follows: 
fliells of an ear-like form, flattiih, almoft wide open, or 
hollow, for, from the apex or head, all along one fide, it 
has only a broad ledge or margin. The apex has alfo a 
fingle perfeiSl whirl ; and a curved row of holes, or per¬ 
forations, runs its length, from the head to the oppofite 
end. Thefe (hells, in appearance and nature, approach 
very nearly to the limpets, and, in like manner, affix 
themlelves to rocks. However, they -cannot truly be 
called iimple, or fliells that are no way fpiral; becaufe at 
their head they have as perfedl and fine a whirl as any tur¬ 
binated (hell: but, as nature in her works has made fuch 
flight tranfitions from one link to another, it is almoft 
impoflible to fix them by human definitions. Thus, fe- 
veral of the chambered limpets have only fach fingle 
whirls 5 and the trocho patella, and cochlea patella, are 
often fo greatly fpiral, as exteriorily to refemble a trochus 
or a fnaii 5 yet they are true limpets. It is therefore im¬ 
poflible to regulate natural obje£ls to a perfect precifion, by 
the molt elaborate and minute definitions. 
The fpiral head of the haliotis has induced many au¬ 
thors not only to feparate them from' the limpets, but 
alio to reject them from the Ample fliells. Thus Lifter 
places them in his Hiltoria Conchyliorum among the tur¬ 
binated (hells, after the nautili, the fnails, and the nerits, 
and preceding the troclii. He does the fame in his work 
de Animalibus Anglias, wherein he fays, it is fpiral at the 
clavicle in the fame manner as other turbinated fliells, and 
therefore by fame is wrongly placed among the Ample 
(hells. Gualtieri ranks them among the fnails with de- 
preffed or flatted clavicles; and Adanfon and Meufchen 
take them from the Ample (hells, and place them as the 
firll family of the fpiral (hells: Dr. Gmelin has placed 
them the laft of the fpiral fliells. Linnaeus allows no (hell 
to be of the haliotis family, without having the row of 
perforations j which is an effential character. Thus the 
Venus ear, ranked by fame as a haliotis, Da Cofta and 
Linnaeus feparate from them. But there is alfo another cha¬ 
racter, which feems to belong to this family ; that is, 
Yol. V. No. 250. 
O L.O G Y. 21 
their infide is always of the fineft or mod orient pearl; 
and even pearls are often bred in them. This is another 
reafon why the Venus ear belongs not to this family, for it 
wants the pearly infide, as well'as the perforations. In 
the row of holes which conftitute thefe perforation?, 
there are generally fix or feven quite perforated, or very 
open ; the reft are clofed, and appear rather like tubercles 
than holes ; for it is (aid the fifti always doles one towards 
the end, as he increafes in fize; and by thefe holes he 
cafts forth his excrements. 
There are but few fpecies of this family. It is even 
doubted, whether fame of thofe propofed by different 
authors, are not rather varieties: but they are found in 
great abundance in mod parts of the world, in their ufual 
and cuftomary kind. Dr. Gmelin enumerates nineteen 
fpecies. There is no inftance on record of a haliotis 
being found foflil. A figure of the haliotis is given in 
the engraving. 
OF CONCAMERATED UNIVALVES. 
The fecond divifion of univalves, contains the conca- 
merated or chambered fliells, that have many regular and 
nearly equidiftant cells or chambers, and a pipe or fi- 
phunculus, that opens into, and communicates from, 
chamber to chamber. This ftrudture forms the effential 
and (pecific character of the (hells of this divifion ; for 
there occur among them not only revolved and turbi¬ 
nated fliells, but even quite Ample, or no-wife turbinated 
ones. The fliells of this conformation confiitute the fifth 
family of univalves, and is divided by Da Cofta into fix 
genera, one genus whereof, viz. the orthoceratites, is of 
a Ample figure; four genera, as the lituitse, or crcziers, 
polythalami, turbines ammonia and ammenoides, are all 
turbinated j and the other genus, or nautilus, is revolved. 
For the arrangement of thefe chambered fliells,’we are 
obliged to have recourfe to the foflil kingdom ; fince 
there are only two genera out of the fix, viz. the lituitcs 
and the nautilus, that are known recent from the fea. 
Yet it is farprizing, that thefe genera, which are found 
foflil in fach amazing abundance all over the globe, and 
form numerous families, have to this hour el'caped the en¬ 
deavours of mankind to obtain them living. Befides 
other reafons that have been given, their being pelagian 
(hells, or (hells that inhabit the very deepeft recedes of 
the fea, feems one principal ca.ufe; as thofe iituations are 
not fabjedt to the agitations of the great tempells, and 
other violent ragings of that immenfe mafs of waters; 
and therefore thele (hells feem conftantly to remain un~ 
difturbed in thofe immenfe deeps. 
The ORTHOCEROS. 
■Thefe are Ample ftraight conical fliells, 110-wife turbi¬ 
nated ; and gradually tapering from a broad end to a 
(harp-pointed top, like a ftraight horn, whence their name. 
They are chambered from bottom to top, and have a fi- 
phunculus, or pipe of communication, from chamber to 
chamber. Planchus, in his book de Conchis minus 110- 
tis littoris Ariminenfis, deferibes fome recent minute 
kinds of this genus, which he found in great quantities 
in the fea fediment, at Rimini, in Italy. The orthocefofes 
he diicovered were fpecies fo very minute, Ids than one 
quarter of an inch, and not thicker than a pin, that they 
demanded the aid of the microfcope to afeertain then* 
ftru&ure. tinnteus, in his order of (hell-fifli, ranks them 
as the nautilus "orthocera. 
How different thefe living fpecies are from thofe found 
foflil, is extremely (hiking; the recent fpecies are fo ve¬ 
ry minute, as to demand the microlcope to examine them ; 
the foflil ones, on the contrary, are mpftly very large, 
frequently above a foot in length, and above an inch and 
a half over; even the final reft kinds, as the alveoli, are 
feldom lefs than an inch long, and a quarter of an inch 
over : and befides their great difference in fize, they no 
wife correl’pond in other particulars with the larger, fo as 
to be imagined young ones of the fame fpecies. J 3 rey- 
G niusj 
