N A U 
in the form of fpots, near the middle of the 
back. The head is covered with large fcales, of 
a more du{]<:y hue than thofe of the reft of the 
body; and the upper jaw is white on each fide, 
with four or five flight black lines crofTing it. 
The chain is yellow, compofed of two large 
fpots of that colour, one placed on each fide of 
the neck, between which appears a triangular foot 
of a deep black, with it's top directed towards 
the tail. It is deftitute of the long canine teeth 
of the viper, and other poilbnous reptiles, by 
means of which the poifon is conveyed into the 
wound; but has two rows of fmall ferrated teeth, 
deftined by nature for the fole purpofe of mafti- 
cation. 
The above minute defcription of this reptile 
feemed necefiary, in order to difcriminate between 
it and the viper, with which it is fometimes con- 
founded. 
NATTER-JACK ; the Rana Rubeta of Lin- 
nsEus. Tliis creature, which frequents dry and 
fandy places, is found on Putney Common ; and 
alfo near Revefby Abbey, in Lincolnfliire, where 
it obtains this appellation. It never leaps; 
nor does it crawl with the flow pace of the toad; 
but it's motions rather refemble running. 
Several of thefe animals are commonly found to- 
gether; and,like the reft of the genus, they generally 
appear in the evenings. The length of the body 
is two inches and a quarter, the breadth being 
one and a quarter; the length of the fore-legs is 
upv/ards of one inch, and that of the hind-legs 
nearly two. The upper part of tlie body is of 
a clirtv vcllow hue, clouded with brown, and 
covered with porous pimples of unequal fizes ; 
and on the back there is a yellow line. The 
under oart of the body is fomewhat paler, and 
marked with black fpots, feeling fomewhat rough; 
the fore-feet are furnifhed vv'ith four divided toes; 
and the hind with five, a little webbed. 
NAVICULA. An appellation given by the 
French conchyologifts to a clafs of fliells, more 
generally known by the name of Nautilus. 
NAUPLIUS. A name fometimes ufed to 
exprefs the nautilus. 
NAUTILUS. A genus of flicll-filh; the 
charaftevs of which are, that the general figure 
of the fiiell fomevv^hat refembles a boat or vefl"el, 
adapted fur fwimming ; but, in the different fpe- 
cies, it is of very various conformation, roundifh 
or oblong, thin or thick, furrowed or flnooth, 
fomxetimes auriculated, and fometimes not. 
Ditferent conchyologifts among the ancients 
and moderns ho.ve denominated this fiiell Nau- 
tilus, from Pilus, Nauplius, Nauticus, Ovum Po- 
lypi, and Polypus Teitaceus; and it is fuppofed 
that men firft diicovered the method of failing 
in veffels from obferving the practice and habits 
of this creature. 
The Nautilus is of tv^o kinds: the one has a 
thin (hell, and generally keeps near the fea-fhore, 
on which it is often th;ov/n by the waves, v/here 
ir frequently quits it's fhell, and periflies; and 
the other either continues in it's fliell like a fnail, 
or feidom ventures out of it; but fometimes 
thrufts out a kind of arms. 
When the former genus is about to fail, it ex- 
tends two of it's jrms aloft, and between thefe 
fupports a mtmbrane, which ,it expands on pur- 
pofe, and fupplies the place of a fail; the two 
other arm.s it i;an^ s out of the fhcll, to ferve oc- 
cafionally either as oars or a fteerage; but this 
N A U 
laft office is generally performed by the tai'. 
When the fea is calm, numbers of thefe creatures 
are frequently feen amufing themfelves with 
failing; but, as foon as a ftorm arifes, or any 
other accident difturbs them, they draw in their 
legs, and fwallowing as much water as will enable 
them to fink, they plunge to the bottom: after- 
wards, when defirous of rifing again, they void 
this abundant water by a number of apertures, 
of which their legs are full. 
The fhell of the other genus is thick, and di- 
vided into forty or more partitions, which grow 
fmaller and fmaller as they approach the extre- 
mity or centre of the fliell; and between each 
of thefe cells and the adjoining one there is a com- 
munication by means of a hole in the centre of 
each partition, through which runs a pipe, the 
whole length of the fifh. 
It is generally fuppofed that this animal occa- 
fionally changes the place of it's refidence by 
moving from one of thofe cells to another, through 
the fmall tube ; but this is by no means probable, 
as it is impofllble to conceive how the body of 
the fifh could be fo much diminifhed or extended, 
as to pafs through the only vifible aperture in 
the fhell. It feems therefore more confonant to 
reafon, to fuppofe that the fifli always occupies 
the largeft chamber in it's fliell; that is, it lives 
in the cavity between the mouth and the firft par- 
tition; and that it never removes out of this; but 
that all the apparatus of cells and a pipe of com- 
munication, which we fo much admire, ferve 
only to admit occafionally air or water into the 
fliell, in fuch proportions as may anfwer the 
creature's demands when inclined either to fink or 
fwim. 
It muft be obferved, that the polypus is by no 
means to be confounded with the thin or paper- 
fhelled Nautilus, notwithftanding the great fimi- 
larity in their arms and bodies; nor is the cornu 
ammonis, fo frequently found foffile, to be con- 
founded with the thick- fhelled Nautilus, though 
the concamerations and general ftru6lure of the 
fhell are both alike ; for there are great and ef- 
fential differences betv/een all thofe kinds. 
The following are fome of die moft curious 
fpecies of the Nautilus clafs. 
Nautilus, Pearl-Shelled. This fpecies ob- 
tains it's name from the beautiful colour of the 
internal furface of it's fhell, which may vie with 
the fineft pearls. It is found in the Archipelago, 
and other feas; and is frequently difcovered foffile 
in the clay-pits and quarries of different parts of 
England. 
Nautilus, Thick, Little. This fhell is of 
a roundifli figure, feidom exceeding one inch and 
a half in diameter. The furface of the whole 
fhell is fmooth ; the opening of the mouth is 
large, and nearly circular, though partly filled 
up behind by the fpiral part of the fljell being 
reverted; the colour of the outfide is a pale tawny 
brown, with lines or ftreaks of a darker hue; 
the infide is bright and perlaceous; and at the 
bottom there is an aperture, running through a 
multitude of cells into which the inner cavity is 
divided. 
The Little Thick Nautilus is found in ths 
Perfian Gulph, and the Oriental feas. 
Nautilus, Thin-Eared. This fpecies is ex- 
tremely beautiful, about ten inches long, and 
furnifhed with a very thin fl-jell. The aperture 
of the mouth is very large, and of an ovated 
fnape^ 
