Of the first sort of teeth are two rows on each side, viz. five in a row, the inward less than the outward, there being twenty in all. In the upper jaw there are only sixteen, viz. five on each side, placed backward, and six before. These do no harm, which was known of old to mountebanks, who, to give a proof of the efficacy of their antidotes, would suffer themselves to be bitten by vipers, but first took care to spoil them of their fangs.

The fangs are placed without the upper jaws, towards the fore part of the mouth, not fastened to the maxillæ, as the other teeth, but the two outmost and largest fangs were fixed to that bone, which may be thought to be the ear-bone; the other fangs, or smaller ones, seemed not fixed to any bone, but rather to muscles and tendons. The fangs were not to be perceived on first opening the mouth, lying couched under a strong membrane or sheath; but so as to make a large rising there on the outside of the smaller teeth of the maxilla; but at pleasure, when alive, the animal can raise them to do execution with, as a cat or lion does its claws. These fangs were hooked and bent, like the tusks of the babyroussa, but some of the smaller ones were bent at right angles; on each side we meet with about six or seven of these. In all these teeth was a pretty large foramen or hole towards the root of it, and towards the point was a plainly visible large slit, sloping like the cut of a pen; the part from the slit being perfectly hollow; and on pressing gently with the finger on the side of the gum, the poison, which was of a yellowish colour, was readily perceived to issue from the hollow of the tooth through the slit.

The vertebræ, according to the figure of the body, were smallest towards both extremes, and largest in the middle. From the neck to the vent there were as many vertebræ as scales on the belly, viz. 168; but from the vent to the setting on of the rattle were twentynine more in number than the scales.

The rattle is well described by Dr. Grew, who observes that it consists of hollow, hard, dry, and semitransparent bones, nearly of the same size and figure; resembling in some degree the shape of the human os sacrum; for although only the last or terminal one seems to have a rigid epiphysis joined to it, yet have every one of them the like; so that the tip of every uppermost bone runs within two of the bones below it; by which artifice they have not only a moveable coherence, but also make a more multiplied sound; each bone hitting against two others at the same time.

The rattle is placed with the broad part perpendicular to the body, and not horizontal; and the first joint is fastened to the last vertebra of the tail by means of a thick muscle under it, as well as by the membranes which unite it to the skin; all the remaining joints are so many extraneous bodies, as it were, or perfectly unconnected to the tail by any other means than their curious insertions into each other.

The number of joints in the rattle of different individuals is very various, from five to twelve, fifteen, twenty, or even, according to some accounts, as many as forty. The pieces of which it consists are successively formed, each having been once attached to the muscle of the last vertebra of the tail, and driven on by the gradual formation of a young or immature one beneath it; but as it is not known whether these successive formations of new joints in the rattle correspond with the general changes of the skin, and as the part is also liable from its nature to occasional mutilations, it cannot be considered as a proper test of the animal's age.

The length of the individual dissected by Dr. Tyson, was four feet five inches; the girth of the body in the largest part six inches and a half; that of the neck three inches, and of the extremity of the tail, near the rattle, two inches.

[Catesby. Tyson. Grew. Phil. Trans. Shaw.

SECTION IX.

Great Boa.

Boa constrictor.-LINN,

The genus boa is remarkable for the vast and almost unlimited size of some of the principal species, which in India, Africa, and South America, are occasionally found of not less than twenty, thirty, and even thirty-five feet in length, and of a strength so prodigious as to be able to destroy cattle, deer, &c. by twisting around them in such a manner as to crush them to death by continued pres. sure *, after which they will swallow them in a very gradual manner;

This practice of larger serpents seems to have been well known to the ancients; thus Lucan, speaking of the monstrous African snakes, (which he also represents as furnished with wings,) tells us they destroy oxen, and even elephants, by writhing around and crushing them to death.

"Vos quoque, qui cunctis innoxia numina terris
Serpitis, aurato nitidi fulgore Dracones,

and when thus gorged with their prey, become almost torpid with repletion, and if discovered in this state, may without much diffi. culty be destroyed by shooting or other methods. There is rea son to suppose, that these gigantic serpents are become less com. mon now than some centuries backwards; and that in proportion as cultivation and population have increased, the larger species of noxious animals have been expelled from the haunts of mankind, and driven into more distant and uncultivated tracts: they are still, however, occasionally seen, and sometimes approach the planta. tions and gardens of the districts nearest to their residence.

Of all the larger Boæ the most conspicuous is the Boa Constric tor, which is at once pre-eminent from superiority of size and beauty of colours: in this respect indeed it appears to be subject to considerable variation from age, sex, and climate, but may be distinguished in every state from the rest of its tribe by the pecu liar pattern or disposition of its variegations. The ground-colour of the whole animal, in the younger specimens, is a yellowish grey, and sometimes even a bright yellow, on which is disposed along the whole length of the back a series of large, chain-like, reddishbrown, and sometimes perfectly red variegations, leaving large open spaces of the ground colour at regular intervals; the largest or principal marks composing the chain-like pattern above mentioned are of a squarish form, accompanied on their exterior sides by large triangular spots, with their points directed downwards;

Pestiferos ardens facit Africa, ducitis altum
Aera cum pennis, armentaque tota secuti
Rumpitis ingentes amplexi verbere tauros.

Nec tutus spatio est Elephas; datis omnia leto;
Nec vobis opus est ad noxia fata veneno."

Ye too, in other climes who harmless rove

In gilded scales, the guardians of the grove,

In horrid Afric's pestilential air

Acquire new natures from the burning glare ;
Ride thro' the blaze of noon on sable wing,
Quick on th' affrighted herds with fury spring;
And gathering all your folds in writhings dire,
Bid the huge ox beneath your crush expire ;
Th' enormous elephant by force can slay,
And need no poison to secure your prey.

The tale of Laocoon, in Virgil, might be also adduced as an example of this particular.