423 
CHap. IV. C O N C ft 
this animal very early attraifted the attention of na- 
turalifts. To its progreffive motion on the furface 
of the ocean, mankind are indebted, it is faid, for the 
firft hint of the art of navigation. This is alluded to 
in the numbers of Pope. 
Learn of the little nautilus to fail, 
Spread the thin oar, and catch the driving gale. 
vitreus. 
cymbiutn . 
cornu . 
arEiica. 
_ 47 
.Nautilus. 
What is the particular organization which enables 
this animal to rife to the lurface or to link to the bot- 
tom at pleafure, feems not to be underftood by natura- 
lilts ; whether it is by throwing out a quantity of wa- 
ter by which it becomes fpecifically lighter than the 
element in which it lives, or by taking in a quantity 
of air, which will produce the fame effeft. It is only 
when the fea is calm and unruffled that the nautilus, 
with his feeble bark, appears on the furface. In rifing 
through the water, the {hell is reverfed, the fharp edge 
of the keel prefenting lefs refiftance to the liquid •, and 
when it reaches the furface, the animal, by exerting its 
arms, reftores it to a proper pofition for its voyage. A 
quantity of water is taken into the fhell to balance it. 
The animal then employs its arms as oars ; or if a gen- 
tle breeze frveep the furface, it flretches two of them 
perpendicularly, by which means the membrane be 4 
tween them is extended in form of a fail ; the other 
arms ferve as oars to direft the courfe, or to keep the 
bark Heady, as well as part of the body which hangs 
over the fhell, and feems to anfwer for a rudder. 
Thus equipped, the folitary navigator glides fmoothly 
along the bofom of the ocean. But, on the approach 
of the fmalleft danger, the appearance of an enemy, 
or the flighted ruffling of the furface of the water, it 
inllantly retires within the lliell, and taking in a quan- 
tity of water, or ejecting a quantity of air, quick as 
thought it finks to the bottom. Mediterranean and In- 
dian ocean. 
2. A. keel of the (hell toothed in the middle. The 
Ihell is conic, tranfverfely ribbed, with a convex keel ; 
aperture oval. It is a very rare fpecies. 
3. A. keel of the lliell vrrinkled, and without teeth •, 
deprefied, thin, wrinkled, with fine longitudinal firs* 
eroding the wrinkles. Mediterranean. 
4. A. keel with 4 fmooth elevated rings ; 1 line 
high, 5 broad. Cape of Good Hope. 
5. A. Ihell perforated, with an entire keel ; 3-J lines 
diameter. Greenland feas, where it is frequently feen 
floating in fpring and autumn. 
Some fpecies of the. argonauta are met with in all cli- 
mates, from the Indian ocean to the Ihores of Greenland. 
Gen. 19. Nautilus. 
Gen. Char . — The nature of the animal which inhabits 
this lliell is not well known. The lliell is univalve, 
divided into feveral compartments, communicating 
by an aperture with each other. 
Species. 
A. Spiral, rounded, with contiguous whorls. 
pompilius. 1 . N. aperture of the Ihell heart-lhaped 5 whorls ob- 
tufe ; fmooth. Indian and African ocean. — This fpe- 
cies is often very large, and it is finely variegated with 
brown flexuous ftreaks, fpots, and marks, under the 
epidermis, which is white j within it exhibits a beauti- 
O L O G Yo 
ful pearly glofs. It is employed for drinking cups by 
the inhabitants of the call. . 
* 2. N. aperture of the Ihell linear ; whorls with el e- calcar. 
vated joints ; minute, white, opaque. Sheppey illand. 
* 3. N. with lateral fpires, with about 20 flexuous, cri/pus* 
crenated joints in the exterior whorl ; marked by ele- 
vated Arise •, aperture femicordate ; fyphon central ; 
very minute. Mediterranean, Sheppey illand, and Sand- 
wich. • 
4. N. aperture obovate ; 4 or 5 volutions, with deep beccarii . . 
fulcated joints ; 10 in the firft fpire, frequent on molt 
Ihores ; minute. 
* 5. N. fimilar to the preceding fpecies, but with theperverfus. 
fpires reverfed. Shores of Britain, frequent. 
* 6. N. fpiral, with fmooth joints ; femipellucid, white, levigalu- 
gloffy •, very minute. Sandwich. lux. 
* 7. N. fpiral, (lightly umbilicated on each fide, 'fA’CadepreJTulus 
many deprefied joints. Reculver, England. Very 
minute, and rare. 
* 8. N. fpiral, umbilicated, -with furrowed joints \utnbilica^~ 
colour opaque, white. Sandw'ich, Minute, not com- tulus. 
mon. 
* 9, R. thick, fpiral, doubly umbilicated, with ^n^craj/ulus. 
joints j opaque, white. Reculver, England. Minute, 
rare. 
* 10. N. fpiral, Job ate; fpires rounded on one £\&e,lobatulus. 
deprefied on the other. Whitftable. 
* 11. N. oblong, carinated ; aperture oval, narrow, carinatu- 
Sandwich. Minute, rare. lus. 
12. N. a little bending, with raifed joints; length fubarcita- 
one-tenth of an inch. tulus. 
* 13. N. comprefled, fubcarinated, fpiral, fmooth, (acujiris. 
gloffy, horn-coloured, with 3 vifible volutions ; dia- 
meter one-fifth of an inch. Brooks, Kent ; marlhes, 
Rotherhithe. Not unfrequent. Lightfoot , Phil. Tranf 
76. Helix nitida, Lin. This is fuppofed to be the 
only fpecies of frelh-water nautilus which has been de- 
feribed. 
14. N. white, convex ; aperture- linear ; firft fpire halthicus. 
Iargeft. Baltic. 
15. N. fpires of the Ihells concealed; very fm all. helicites. 
Found in a fulfil ftate on St Peter’s mountain at Mae- 
ftricht. 
16. N. aperture linear ; fpires comprefled, with rugofus* 
thickened margins. Southern ocean. Very fmall. 
17. N. aperture comprefled, linear; fpires compref- umbilica° 
fed ; umbilicus concave ; minute. Croatia. tus. 
B. Spiral, rounded, with feparate whirls. 
18. N. aperture orbicular ; whirl cylindrical; on efpicula, 
inch in diameter, American and Indian oceans. 
19. N. imooth, with 4 conic tubercles; very mi -fpengleru 
nute. India. 
20. N. diaphanous, middle partitions protuberant unguicula* 
outwards; furface with fix conic tubercles; minute, tor. 
India. 
C. Elongated, and nearly Jlraight. 
* 21. N. incurved, fpiral at the tip ; whirls conUgxs- femilituux, 
ous ; minute, convex ; the partitions appearing out- 
wardly. Croatia, Sandwich. Rare. 
22. N. fubconic ; globular divilions growing gra -lituus. 
dually lefs ; tip incurved, fpiral. Red fea. Frequent- 
ly found foffil. 
23- N. with a flight curvature; divilions obliquely obliqvus. 
firiatefi; 
