40 CONCH 
thirty different fpecies of the cornua ammonis. They lie 
immerfed in a bluifh foflll ftone, of a foft texture and 
fatty appearance, in prodigious numbers, 'and of a great 
variety of fizes, > from the larger forts down to fuch as 
could not be feen without very accurate inipeftion. Such 
as lie in the fofteft of thefe ftones are foft like their ma¬ 
trix, and eafily crumble to pieces ; others are harder. In 
a piece of this ftone, of the bignefs of a finger, it is com¬ 
mon to find thirty or more of thefe foflils; and often they 
are feen only in form of white fpecks, fo minute that their 
figure cannot be diftinguifhed till examined by the micro- 
Icope. They all eonlift of feveral fpirals, which are dif¬ 
ferent in number in the different fpecies, and their ftriae 
alfo are extremely various; fome very deep with high 
ridges between them, others very flight; fome ftraight, 
others crooked; others undulated, and fome terminating 
5 m dots, tubercles, or cavities, towards the back, and 
others having tubercles in two or three places. They are 
all compofed of a great number of chambers or cells, in 
the manner of the nautilus pompilius, each having a 
communication with the others, by means of a pipe or 
fiphunculus. A few of the fmall fpecies have been fiflied 
up alive; but the large and beautifully marked ones are 
found only foflil. They are compoled of various foffii 
bodies, often of quarry ftone, fometimes of the matter of 
the common pyrites, and of a great variety of other fub- 
ftances; and though they appear ufually mere ftones, yet 
in fome the pearly part of the original (hell is preferved 
in all its beauty. Sometimes alfo, while the outer fub- 
ftance is of the matter of the pyrites, or other coarfe, 
ftony, or mineral, matter, the inner cavity is filled with a 
pure white fpar of the common plated texture. This gives 
a great beauty to the fpecimens, many of which are dug 
out of the alum rocks in Yorkfliire. 
M. de Lamanon, a French naturalift, who accompa¬ 
nied La Peroufe in hij late voyages of difcovery, feems 
to agree with moft conchologifts, that the larger cornua 
ammonis may (till exift in the fea; but he thinks they are 
in very fmall number, and materially different from the 
greater part of the foflil ffiells above defcribed. He con¬ 
tends that thofe ought to be Confidered as a race, for¬ 
merly the moft numerous of all, of which, either there 
are no defendants, or thofe defendants are reduced to 
a very few degenerate individuals. That there are no 
living animals with (hells of the very fame kind with fome 
of the foffii cornua ammonis, the following oblervations 
he confiders as a fufficient demonftration :—“ The foffii 
fhells are very light and thin, whereas the fhells of thofe 
animals that live in very deep water are always thick and 
ponderous; belides, the form of the foffii cornua ammo¬ 
nis points out to us, in fome meafure, the organization 
of the animal which inhabited it. The celebrated Juflieu 
proved, in 1721, that there exifted a very clofe analogy 
between the ammonite and nautilus. It is well known 
that the nautilus, by filling or emptying a part of its (hell, 
has the power of remaining ftationary in any depth it 
pleafes: the fame was doubtlefs the cafe with the ammo¬ 
nite ; and if this fpecies (till abounds in the lea, it would 
1 'urely be occafionally difeovered by bailors. The waves 
alfo would throw fragments of it on the fliore ; fifliermen 
might fometimes entangle it in their nets; or, at leaft, 
there would be fragments (ticking to the lead of the 
founding-line when afeertaining great depths. It may 
alfo be added, that if the ammonites never quitted the 
abyfs of the fea, thofe which are found petrified would 
not be conftantly met with on the fame level, and in the 
fame bed, as thofe fheil-fifh that only inhabit the (hallows. 
Yet there are found, in a multitude of places, ammonites 
mixed with turbines, buccina, and other littoral fhells. 
They are found, befides, at every degree of elevation 
from below the level of the fea to the ftimmits of the 
higheft mountains. Analogy alfo leads us to fuppofe, 
that nature, who lias given eyes to the nautilus, has not 
refufed them to the ammonite : now what ufe could thefe 
,be of if they remained confined to thofe depths which the 
OLOGY, 
light is unable tp penetrate. The extinfHon of the an¬ 
cient race of ammonites is therefore a faff, which no ra¬ 
tional fuppofition can deftroy; and this fa£t is undoubt¬ 
edly the moft furprifing of any that is prefented to us is. 
the hiftory cf aquatic animals. The difcovery of a few 
living, fpecies of cornua ammonis does not deftroy the 
truth of this, for thefe ammonites are very different from 
thofe which are found petrified. They are extremely rare, 
and cannot be looked up to as the reprefentatives of the 
old ammonites, fo varied in their fpecies, and the number 
of which in the ancient ocean was probably far more con- 
fiderable than that of all the other (hells befides.” 
To every univalve (hell, rolled in a fpiral, fo as that 
a horizontal plane will divide it into two equal parts, 
formed of united fpirals, and bearing a certain proportion 
to each other, this author gives the name of an ammonite. 
“ I thought it abfolutely neceffary,” fays he, “ to afeer- 
tain the precife meaning of the term ammonite., previous to 
deferibing that which I found during our voyage round 
the world. The form of this is almolt orbicular, thedong 
diameter being to the fhort one as three lines to two lines 
and three quarters. A line is the twelfth part of an inch. 
The firft fpire is by far the largeft, occupying nearly half 
of the longitudinal diameter. The fummit is placed at 
the diftance of about two-thirds of this diameter; it is 
terminated on the right fide by a very fmall knob, vifible 
only through a magnifier, thus differing from the ammo¬ 
nite of Rimini, (mentioned in p. 22,) which befides is 
microfcopical and celled, the infide of this which we are 
now- fpeaking of being entirely plain. The number of 
fpiral circumvolutions is four and a half; they are equally 
convex on both Tides, and are fixed on a plane, dividing 
the (hell into two equal parts; there is on each fide a kind 
of bofs formed by the increafe of the perpendicular dia¬ 
meter of the fpires, in proportion as they recede from the 
center. The furface is fmooth ; the back is armed with 
a flat, even, brittle creft, as thin as paper, furrounding it 
on every fide like a rufF: it is about half a line bioad, 
extends over the fummit of the fpires, and ferves to join 
them together. The mouth of the (hell is nearly trian¬ 
gular; its edges projefl in the form of lips, and are rounded 
at the border. I have often found this ammonite enclofed 
in the ftomach of the ('comber pelamis, or bonetta, caught 
in the South Sea, between the tropics, where no bottom 
was found with a line of more than two hundred fathoms. 
Thefe fhells were covered with a black clayey mud. Their 
fize varies from one to four lines acrofs; they are con- 
fequently the largeft living ammonites that have yet been 
difeovered.” 
The above reafoning, however, in fupport of the ex- 
tinflion of the foffii ammonia, feems far from conclufive, 
and by no means eftablifhes the fa£t in queftion. How 
many fpecies of teltaceous animals have been lately difeo¬ 
vered, that have eluded the refearches of mankind for 
thoufands of years before? and how many may yet re¬ 
main in the depths of the ocean, totally unknown to man, 
dwelling perhaps in a tranquil ftate, with the maturer 
cornua ammonis ? That no fragments of thefe fhells in a 
recent ftate are no.w ever found upon the fea-coafts of any 
country, is no good argument to prove their fton-exift- 
ence; becaufe nothing lefs than a convulfionof the globe, 
fufficiently powerful to overturn the bottom of the fea, 
can caff on fliore thefe pelagian (hells; for the fame parity 
of reafon that no convulfion of nature, lefs univerfal than 
the general deluge, could have heaped up, promifcuoufly 
together, the foffii fhells we now find on the moft elevated 
fummits, and in fituations far removed from the places 
of their natural and primeval abode. M. de Lamanon 
feems anxious to prove, that the ancient ammonites did 
not inhabit great depths of the fea; and that Linnaeus 
was deceived when he fuppofed that in great depths they 
may ftill be found. But this naturalift contradifts liim- 
felf, and entirely does away his own argument, when he 
tells us, that he could never find the recent ammonites 
but in the South Sea, where no bottom was to be found 
with 
