23 
CONCHOLOG.Y, 
appear externally, but lie latent or quite hidden within 
the body of the (hell : Turbinata, volutas apice non emi- 
nente, vel clavicula intus recondita. The nautili are of 
a chambered ftruftuire ; the partitions of the cells or 
chambers being- concave-convex roundifh plates. How¬ 
ever, there are t'oflil kinds with foliaceous futures like the 
ammonitse;' w’hich implies, that all the fpecies have not 
fuch regularly round partitions : and, indeed, Breynius, 
on this account, divides the.nautili into two orders; thofe 
with concave-convex femilunar diaphragms, and thole 
with jagged or finuated diaphragms. 
The paper nautile, though claffcd by mod: authors as 
a nautilus, i6 of a different genus, as not being of a cham¬ 
bered lfruiibure. Authors make two varieties'of the Eaft 
Indian or pearly kind, viz. the umbilicated and the non- 
umbilicated ; but Gmelin confiders them as the fame ani¬ 
mal, and places them both under the 1'pecific name of 
nautilus pompilius. This is by feveral authors erroneoully 
called nautilus Greecorum ; whereas the nautilus of the 
Greeks was the paper nautilus, or argonaut. 
The animal belonging to this (hell is faid to inhabit 
only the uppermolt or open chamber, which is much 
larger than the reft. The others remain empty, except 
that the pipe, or fiphunculns,. which communicates from 
chamber to chamber, is filled with an appendage or tail 
of the animal, Like a gut or firing. The fiphunculus is a 
dilatable tube under the command of the animal. When 
it is dilated, like the fwimming-bladder of a filh, it ren¬ 
ders the nautilus buoyant. When it is contracted, the 
fifth and Ihell fink, and juft to fuch a degree as the prefent 
occafions of the animal require. 
Thereare two remarkable foffil kinds of nautili yet un- 
difcovered in a living (tate, viz. One about the fize of a 
pippin, quite pyritical, without the flighted veftiges of 
the natural (hell. It is deeply umbilicated, has fine folia¬ 
ceous futures in feveral parts, and is thickly and finely 
ridged acrofs from fide to fide ; the ridges not ltraight, 
but curved, the curvature tending downwards, or from 
the mouth. The other, a fmall kind, with undulated fu¬ 
tures, found in the limeftone of Derbyfbire, and in Ger¬ 
many. , 
The nautilus has been always efteemed, as well for the 
elegance of its fheil, as for the beautiful mother of pearl 
which it produces. Fig. 9, in the fecond plate of con- 
choiogy, exhibits Knorr’s correCt drawing of this (hell,in 
its, natural ftate. The ground-colour is a yellowifli-white, 
approaching, at the extremities to a light orange. In 
the center it is radiated with flame-colour, from whence 
proceed ftriated irregular bands of deep red in all direc¬ 
tions. The infide is lined with molt beautiful pearl. 
The black which riles over the fpiral concamerations is 
perfectly natural, and is occalioned by a mucous matter 
which the animal throws out, fimilar to the cuttle-fifli. 
The bottom of the (hell is rounded in a beautiful form, 
and meafures about a foot and a half in diameter; and is 
of the thicknefs of a half-crown piece. It inhabits the 
Indian ocean, and is found on the (bores of Africa, parti¬ 
cularly near the Cape of Good Hope, where, quickly af¬ 
ter a ltorm, they are feen to l'wim about in conflderable 
numbers, and are then taken only by the molt expert 
fifth ermen. 
The fuperb cordated ftruCture of the interior part, with 
its materials of orient pearl, has induced us to give the 
Conchology -Plate III. for the more perfect illuftration of 
this celebrated fheil. Fig. 1, reprefents the (hell with its 
exterior lamina or covering taken off, to drew the beauti¬ 
ful pearl of which the interior l'ubltaace is compofed. A 
filvery luftre, with undulating waves, on which a pale de¬ 
licate red expands itl'elf, and at every movement changes 
to a different colour, gives this ftieil a magnificent ap¬ 
pearance. Formerly artilts fpent much time in working 
thefe fllells, to increafe their beauty, either by decora¬ 
tions in bals-relief; or by fimpiy engraving lines, which 
they rubbed over with various tints. Hence we often 
find thefe (hells ornamented with emblematical figures, 
4 
fucli as the bacchanals, hunting, fiflring, foliage, fymbols« 
arms, crelts, and other decorations. Sometimes they are 
mounted with gold or filver, and converted into drinking 
veffels; for they will hold more than a quart. In the fi¬ 
gure there is a large brown fpot in the middie of the 
(hell, which it is neceflary to explain, becaufe it furniflies 
a character, by which the nautile is diftinguifthed from 
the cornu ammonia. In all the latter, the circles are ap¬ 
parent iff the lame place near the center of the firft. 
whirl; but the nautile has the (hell clofed. Fig. 2, re¬ 
prefents an infide view of the fame fheil, whereby the cor¬ 
dated work, and all the partitions, may be feen, even to 
the fmalleft, which is in the center. It is to that only 
that the animal is fattened by a tendon. This tendon 
paffes through all the divifion9, in a fiphon, fattened in 
the middle of the partitions, quite to the principal one, 
which is the largelt, and properly the animal’s abode. 
The other partitions do not appear to be of much real 
ufe to the fifh; for it has never been found in any of 
them. The fle(hy part, or body of the animal, fills up 
all the interior of the largeft chamber; but at the ap¬ 
proach of danger, or when it perceives an enemy, it con¬ 
tracts itfelf into a very fmall fold, and lies hid below the 
fheil. There may be forne doubt whether the tendon 
which paffes through the partitions, does not receive a 
great part of the animal’s interior fubftance on thefe oc¬ 
cafions; which circumftance feems neceffarily to follow 
from the diminution of the body. 
Of REFOLDED UNIVALVES. 
Revolved (hells are thofe whole fpires are latent, or hid¬ 
den within the body, and do not in any manner appear 
externally ; fo that they have no clavicle or turban. The 
nautilus pompilius is alfo a revolved fheil; but, being 
more remarkable for its chambered ftruCLure, it is ar¬ 
ranged in the preceding clafs. “This divifion contains the 
fixth family of the univalves, which Da Colta forms into 
three genera, viz. nuces or bullae, the pewit’s eggs, or 
dipping fnails; femiporcellanae, or (hells nearly refembling 
the porcellains ; cypreae or porcellanas, the cowries. 
BULLA, the DIPPER, or PEWIT’S EGG. 
The firft genus, or bullae, befides their common names 
of pewit’s eggs, and dippers, are alfo called fea-nuts . The 
definition of this genus is as follows: they are moltly of 
an oval fhape, and umbilicated at the bottom. The mouth 
is very patulous, efpecially at the top, for it narrows 
greatly downwards. The lip is thin, (harp, and naked, 
or without any border or other work; and with a fmall 
facing or columeila lip on the upper part of the mouth. 
The arrangement of this genus is much confufed in au¬ 
thors, by their feeming connedtion with the two follow¬ 
ing genera of femiporcellanas and cypreae. Lifter makes 
them a genus of cowry, and calls it concha veneris baft 
umbilicatd. Grew andBuonanni place it with the fnails. 
Rumphius, with his cochleae globofas; Argenville, Da¬ 
vila, and Meufchen, do the fame ; and, indeed, Linnaeus’s 
genus of bulla includes the figs, turnips, &c. as w>ell as 
the dippers. Gualtieri makes it a genus preceding the 
cowries, and following the paper nautilus. 
The arrangement that Rumphius, Argenville, Lin¬ 
naeus, Davila, and Meufchen, give them as cochleae glo- 
bofae, or tuns, is very furprifmg, and extremely errone¬ 
ous; fince they have a very different effcntial character, 
though all have patulous or very large mouths. For the 
nuces, or bullae, like the cowries, have no clavicle or tur¬ 
ban, becaule their fpires lie within their bodies ; whereas 
the conchas globolse, as the partridges, tuns, &c. are re¬ 
ally turbinated (hells, and have a very fair and llrong ex¬ 
ternal clavicle ; but it is generally flattifh, or not much 
produced. Though there is a vaft difference of colouring 
in the dippers, it feems, nrverthelefs, that they are only 
varieties, and that this genus is not numerous. The 
Conchology-Plate IV. exhibits fpecimens of thefe dip- 
ping-fhells, or pewit’s eggs, from beba. 
The. 
