322 
O T I 
O S T 
fill whether they should be considered as 
truly distinct, or as constituting mere sexual 
differences. 
The triquetral trunk-fish measures about 
twelve inches in length, and is, as its name 
imports, of a trigonal shape, the sides slop- 
ing obliquely from the ridge of the back, 
and the abdomen being flat ; the whole ani- 
mal, except to within a -small distance from 
the tail, is completely enveloped in a bony 
covering, divided into well-defined hexago- 
nal spaces, and covered (as in the whole 
genus) with a transparent epidermis like that 
of the armadillo among quadrupeds ; the 
usual colour is a subferruginpus brown, with 
a white spot in the centre of each hexagon, 
which is also marked by fine rays diverging 
from the centre to the edges : the tins are 
yellowish, and the tail rounded ; the naked 
part of the extremity of the body or base of 
the tail being marked with white specks, 
similar to those on the crustaceous part of 
the animal : the pectoral fins are rather small 
than large, and of a rounded shape : the dor- 
sal and anal are also rather small, and are 
situated opposite each other towards the ex- 
tremity of the body, and, like the rest of the 
genus, this lisk is destitute of ventral lins. 
It is a native of the Indian and American 
seas, and is supposed to feed on the smaller 
Crustacea, shell-fish, and sea-worms. It is 
said to be considered as an excellent fish 
for the table, and is held in high estimation 
among the East Indians. There are ten 
species. 
2. Ostracion quadricornis, four-horned 
trunk-fish ; length twelve inches ; shape sub- 
trigonal ; the back, when viewed in profile, 
strongly arched, and having a smooth outline ; 
mail divided into large hexagons marked with 
numerous and very small tubercles ; ou 
the top of the head' two very strong spines 
pointing forwards ; and from the hind 
part of the abdomen, immediately be- 
fore the anal fin, two more spines pointing 
backwards ; colour of the mailed part sub- 
violaceous brown, with darker streaks irre- 
gularly dispersed over the whole; naked 
part of the body near the tail, yellowish- 
brown, marked with deep-brown spots ; fins 
and tail yellowish-brown. Native ot the 
Indian and American seas. See Plate Nat. 
Hist. fig. 304. 
OSTREA, the oyster, in zoology, a genus 
belonging to the order of vermes testacea. 
'The shell has two unequal valves ; the cardo 
has no teeth, hut a small hollowed one with 
transverse lateral streaks. There are thirty- 
one species, principally distinguished by pe- 
culiarities in their shells. The common oys- 
ter is reckoned an excellent food ; and is 
eaten both raw and variously prepared. 
The character of the genus, in the words of 
Barbut, is, “ The animal a tethys ; the shell 
bivalve, unequivalve, with something like 
ears ; the hinge void of teeth, with a deep 
oval hole, and transverse streaks on the 
sides. There is no womb nor anus.” The 
genus is divided into four families, of which 
ostrea is the last. 
The oyster differs from the muscle in 
being utterly unable to change its situation. 
It is entirely without a tongue which an- 
swers the purposes of an arm in the other 
animal, but nevertheless is often attach- 
ed very firmly to any object it happens to 
approach. Nothing is so common in the 
rivers of the tropical climates, as to see ovs- j 
ters growing even amidst the branches of j 
the forest. Many trees, which grow along i 
the banks of the stream, often bend their 
branches into the water, and particularly 
the mangrove, which chiefly delights in a 
moist situation. To these the oysters hang 
in clusters, like apples upon the most fertile 
trees ; and in proportion as the weight of the 
fish sinks the plant into the water, where it 
still continues growing, the number of oys- 
ters encrease, and hang upon the branches. 
This is effected by means of a glue proper 
to themselves, which when it cements, the 
joining is as hard as the shell, and is as dif- 
ficultly broken. 
Oysters usually cast their spawn in May, 
which at first appears like drops of candle- 
grease, and sticks to any hard substance it 
falls upon. These are covered with a shell 
in two or three days ; and in three years the 
animal is large enough to be brought to 
market. As they invariably remain in the 
places where they are laid, and as they grow 
without any other seeming food than the af- 
flux of sea-water, it is the custom at Col- 
chester, and other parts of England, where 
the tide settles in marshes on land, to pick 
up great quantities of small oysters along 
the shore, which, when first gathered, seldom 
exceed the size of sixpence. These are 
deposited in beds where the tide comes in, 
and in two or three years grow to a toler- 
able size. They are said to be better tasted 
for being thus sheltered from the agitations 
of the deep ; and a mixture of fresh water 
entering into these repositories, is said to 
improve their flavour, and increase their 
growth and fatness. 
The oysters, however, which are prepared 
in this manner, are by no means so large as 
those found sticking to rocks at the bottom 
of the sea, usually called rock-oysters. 
These are sometimes found as broad as a 
plate, and are admired by some as excellent 
food. But what is the size of these com- 
pared to the oysters of the East Indies, some 
of whose shells have been seen two feet 
over ! The oysters found along the coast of 
Coromandel, are capable of furnishing a 
plentiful meal for eight or ten men ; but 
it seems universally agreed that they are no 
way comparable to ours for delicacy of fla- 
vour. 
OSTRICH. See Struthio. 
OSYRIS, poet’s rosemary, a genus of the 
dicecia triandria class of plants, without any 
flower-petals ; the fruit is a globose unilocu- 
lar berry, containing a single osseous seed. 
There are two species. This whole shrub 
is astringent, and consequently good in 
fluxes. 
OTIIERA, a genus of the tetrandria mo- 
nogynia class and order. The cal. is four- 
parted; pet. four; stigma sessile; caps. 
There is one species, a shrub of Japan. 
OTHONNA, a genus of the polvgamia 
necessaria order, in the syngenesia class of 
plants ; and in the natural method ranking 
under the 49tn order, composite. The re- 
ceptacle is naked; there is almost no pap- 
pus ; the calyx is monop hyllous, mnltifid, 
and nearly cylindrical. There are 27 spe- 
cies. 
OTIS, the bustard, in ornithology, a dis- 
tinct genus of birds, of the order of the gal- 
O V I 
lina*, the characters of which are these : there 
are three toes on each foot, all turned for- 
wards ; and the head is naked, or has no 
comb. There are four species, principally 
distinguished by their colour. Owe of the spe- 
cies, the tarda, or bustard (see Plate Nat. 
Hist. tig. 305.), is the largest of the British 
land fowl, the male at a medium weighing 
25 pounds ; there are instances of some very 
old ones weighing 27 : the breadth nine 
feet ; the length near four. Besides the size 
and difference of colour, the male is distin- 
guished from the female by a tuft of feathers 
about live inches long on each side of the 
lower mandible. Its neck and head are ash- 
coloured ; the back is barred transversely 
with black, and bright rust-colour; the greater 
quill-feathers are black; the belly white; 
the tail is marked with broad red and black 
bars, and consists of twenty feathers ; the 
legs dusky. 
The female is about half the size of the 
male : the crown of the head is of a deep 
orange, traversed with black lines ; the rest 
of the head is brown. The lower part of the 
fore-side of the neck is _ ash-coloured ; in 
other respects it resembles the male, only 
the colours of the back and wings are more 
dull. 
The birds inhabit most of the open coun- 
tries of the souih and east parts of this is- 
land, from Dorsetshire as far as the Wolds 
in Yorkshire. They are exceedingly shy, 
and difficult to be shot ; run very fast ; and 
when on the wing can fly, though slowly, 
many miles without resting. It is said, that 
they take flight with difficulty, and are some- 
times run down with greyhounds. They keep 
near their old haunts, seldom wandering 
above twenty or thirty miles. Their food 
is corn and other vegetables, and those large 
earth-worms that appear in great quantities 
on the downs before sun-rising in the sum- 
mer. These are replete with moisture, an- 
swer the purpose of liquids, and enable 
them to live long without drinking on those 
extensive and dry tracts. Besides this, na- 
ture has given the males an admirable ma- 
gazine for their security against drought, 
being a pouch whose entrance lies immedi- 
ately under the tongue, and which is capable 
of bolding near seven quarts; and this they 
probably till with water, to supply the hen 
when sitting, or the young before they can 
fly. Bustards lay only two eggs of the size 
of those of a goose, of a pale olive-brown, 
marked with spots of a dark colour ; they 
make no nest, only scrape a hole in the 
ground. In autumn they are (in Wiltshire) 
generally found in large turnip-fields near the 
downs, and in flocks of 50 or more. 
OTTER. See Mustela. 
OVAL, an oblong curvilinear figure, 
otherwise called ellipsis. The proper oval, 
however, or egg-shape, differs considerably 
from that of the ellipsis, being an irregular 
figure, narrower at one end than at the 
other ; whereas the ellipsis, or mathematical 
oval, is equally broad at each end ; though 
it must be owned, these two are commonly 
confounded together, even geometricians 
calling the oval a false ellipsis. 
OVARIES. See Anatomy, and Com- 
parative Anatomy. 
OVIEDA,a genus of the didynamia angio- 
