ARC 
* Aracari!' It confiderably refembles the toucan, 
or Brazilian pye; and, from the conformation of 
it's feet, feems evidently of the woodpecker kind. 
ARACHNOIDES. The name of one of the 
genera of the echini marini : the diftinguifhing 
characters of which are, that it is of a circular 
form, but varioufly indented at the edges; the 
mouth is round, and placed at the centre of the bafe ; 
and the aperture for the anus is quadrangular, and 
fituated in one of the fides on the fuperior fuper- 
ficies, but near the edge. 
ARANEA. A genus of the aptera infefts, in 
theLinnjEan fyftem. See Spider. 
ARANEA CONCHA. The name of a genus 
of fea-ftiell, of which there are feveral fpecies; ufu- 
aily diftinguifhed in England by the name of fpi- 
der-fh^ells. They belong to the family of murex, 
and their peculiar charafler is the having digitated 
lips. The feveral fpecies have different numbers of 
fingers, from the lip of the fliell, as four, five, fix, 
feven, and eight. 
ARANEUS MARINUS; The fea-fpider ; a 
name by v/hich fome naturalifcs have exprefled the 
fifh more ufually called draco marinus, which is 
fuppofed to contain fome venomous qualities in the 
fpines of it's dorfal bone. 
ARARAUNA. A name given by Marcgrave 
to a Brazilian bird of the macaw kind, but of a 
different colour. The bill is black, and the eyes 
are a fine fky blue, with black pupils : the flcin 
round the eyes is marked with black and white 
fpots ; and the legs and feet are brown. On the 
fore-part of the head is a kind of cap, confifting of 
fine green plumage ; and, under the throat, a circle 
of black feathers. The fides of the neck, the breaft, 
and the lower part of the belly, are yellow: but the 
hinder part of the head, as well as the neck, back, 
and wings, are all blue; except that the extremity 
of the latter is mixed with yellow. The tail is 
beautifully intermixed with long blue and yellow 
feathers, but in general all the external blue fea- 
thers are internally black. 
ARC^, or ARKS. A family of Ihells of the 
bivalve kind, fometimes called boats, having their 
hinges on a perfefl ftraight line, and being of a 
fbmewhat fquarifh figure, or rather oblong, like 
the Noah's Arks and fquare cockles. 
Conchologifts affign difi^erent ranks to the Arks: 
Lifter inferts them among the multarticulate 
cockles ; placing the Noah's Ai-ks among the muf- 
cles, as many-toothed mufcles. Woodward ranks 
them among his polyginglymi forma oblonga ; 
Argenvilie places them in his fourth family, or 
that of heart-cockles ; Davila makes them a dif- 
tindl genus of his fourth family, or heart-cockles, 
and gives them the name of Arks; and Linnaeus 
ranks them as a diftin6l genus, and calls them Area. 
This family,however, contains but a very fe w fpecies . 
ARCHITALASSUS. A name given by fome 
authors to that beautiful and precious fliell -called 
by us the admiral. 
' ARCTIC BIRD, AMERICAN. This bird is 
fomewhat larger than a tame pigeon, and has a bill 
comprefled fidev/ays, hooked at the point, with a 
nail at the extremity, vv^hich is feparated from the 
other part by a crols furrow. The top of the head is 
blackifli, and the fides of the head, the throat, neck, 
breaft, and belly, are white ; but the legs and lower- 
belly are cinereous. The lower part of the neck 
behind, as well as the whole back, wings, and tail, 
are likewife of a dark cinereous colour. The tail- 
feathers are fhorteft on the fideSj and gradually in- 
A R G 
creafe in length to the tv/o centre ones ; which arc 
very confiderably longer, and referable thofe of a 
man-of-war bird. The legs, which appear weak, 
are bare of feathers above the knees, and of a bright 
yellow colour. The feet are black, and the three 
forward toes are webbed like thofe of a duck. This 
bird is a native ofHudfon's Bay; and Edwards 
■ confiders it as a diftinft fpecies. 
ARDEA. A genus of the order of grallas, be- 
longing to the clafs of aves, in the Linnsean fyf- 
tem : it's diftinguifliing chara6ters are, that the beak 
is ftraight, acute, long, and comprefi^ed ; a fulcus 
or furrow pafling from the noftrils, which are li- 
near, to the apex; and the feet are furnifhed with 
four toes. Linnaeus enumerates twenty-fix fpecies 
of this genus. 
ARDEOLA. A very beautiful Brazilian bird 
of the heron kind, but not larger than a pigeon. 
ARENARIA. A bird ufually known in Eng- 
land by the name of the fanderling, and in ibme 
places, particularly in Cornwall, by that of thecur- 
willet. It is a water-bird of the long-legged, open- 
footed kind, and is a fize larger than the tringa mi- 
nor, or fand-piper. This fpecies frequents the fea- 
fhore, and fiies about in large flocks. 
ARGENT AND SABLE. A very curious 
white moth beautifully chequered and fpotted 
with black; the expanfion of the wings being 
about an inch and a half. The caterpillar feeds 
on white-thorn, and changes to a chryfalis about 
the firft week in May; but both the caterpillar 
and chryfalis are fo exceedingly fcarce, that the 
moft inquifitive aurelian has never been able to 
difcover either of them ; and, indeed, the moth it- 
felf is feldom feen in this country. It feems to be 
a native of the woods, or lanes, where it is fome- 
times caught about the beginning of June. In fome 
particular feafons this admired Tnfed" is found in 
great plenty, and feems to breed with amazing fe- 
cundity; but then the fpecies again become ex- 
tremely fcarce, and feveral years elapfe before they 
are again feen in any numbers. 
ARGENTINA. The name of a genus of fiih 
of the malacopterigious kind; and, in the Linnsan 
fyftem, of the order of abdominales ; the characters 
of which, according to Artedi's definition, are thefe: 
the body is oblong and cylindric ; and the teeth are 
placed on the tongue and palate. There appears, 
however, from the fame author, to be only one fpe- 
cies of this genus, which is furnifhed with large 
eyes, and a bifid tail, and is caught on feveral of the 
Italian fhores. Ray defcribes the Argentina to be a 
finallfifhof thelarengiform kind, caught in the Me- 
diterranean, and common in the markets of Rome. 
This fifli, which has fometimes been caught on the 
Britifh coaft, is about three inches long ; the eyes are 
large, and the irides filvery. The lower-jaw has 
a confiderable fiope ; the teeth are very fmall ; the 
body is compreffed, and almoft of an equal deptli 
to the anal fin; and the tail is forked. The back 
is of a dufky green colour; and the fides and coverts 
of the gills appear as if overlaid with filver. On 
each fide of the belly is a row of circular pundlures ; 
and above them there is another which terminates 
near the vent. 
ARGONAUT A. A genus of worms of the 
teftacea order; the animal of which is a fepia; and 
the fhell is univalve, fpii-al, membranaceous, and 
fingle-celled. There are only two fpecies of this 
genus. 
ARGUS. An animal of Iceland, remarkable 
for it's number of eyes, and in that country called 
ofcabicorn. 
