102 Perennibkanchiate Amphibia. REPTILES. Perennibranchiate Asiphibia. 
kept in a vessel containing a large quantity of water, 
or in which the water is frequently changed, it mani- 
fests but little disposition to rise to the surface for 
atmospheric air ; but when the quantity of water is 
small, or not often changed, it soon finds the air in the 
water insufficient for its purposes, when it ascends to 
the surface, takes a mouthful of air, and sinks again 
with it to the bottom.” 
In the second family of this order, the Sirenida:, 
we have only space to mention particularly one species. 
This is well known by the name of the Mud-eel. 
THE MUD-EEL or Siren {Sirenlacertina ) — represented 
in Plate 4, fig. 1 — is a native of South Carolina and 
Georgia, and is about nineteen inches in length, and 
even sometimes reaches two feet, while it measures 
four or five inches in circumference. In its general 
form and aspect it bears a great resemblance to an 
eel, and the surface of the body is very smooth and 
slimy. The tail is long and compressed, and is mar- 
gined for several inches both above and below by a 
narrow, rayless fin, which greatly assists it in moving 
through the water. It is of a deep blackish-brown 
colour, rather paler beneath, where it is partially 
tinged with a bluish hue, with a tinge of violet, and is 
marked all over with numerous small white or milky 
spots. The head is rather small for the size of the 
animal, is depressed, of a suboval form, and the muzzle 
is blunt and flattened. The mouth is not wide, but is 
covered with tolerably thick lips. The nostrils are 
small, placed near the anterior angle of the upper jaw, 
and the eyes are very small, dim, of a blackish colour, 
and covered with a prolongation of the skin. The 
gills, according to the late Mr. James Wilson, to whose 
memoir we refer the reader, consist of three fleshy 
peduncles, which increase in size from the first to 
the last. They are beautifully branched from beneath, 
and along their lateral and terminal edges ; and these 
little branches are divided and subdivided into still 
more minute ramifications. This elegant fringe-work 
forms the true gills, the central and fleshy stalks serv- 
ing merely as their support. Beneath, and rather in 
advance of these bodies, are three nearly vertical 
clefts, through which the water is ejected backwards 
from the inside of the mouth upon the gills, though 
with a much more languid and less perceptible action 
than in fishes. The feet are only two in number, the 
anterior pair ; they are but slightly developed, how- 
ever, and of little service, if any, in progressive motion. 
They are in constant motion, as the animal moves from 
place to place on land, and are folded back when it 
swims in the water. They are each terminated by 
four toes, the extremities of which are rather pointed, 
* slightly curved, and terminate in semi-corneous tips. 
This animal, as its English name indicates, lives chiefly 
in mud, and, according to Mr. Holbrook, is abundant 
in the rice-fields of Carolina. “ It is often thrown 
out,” he says, “ in great numbers, at certain seasons, 
when the ditches are cleaned. Being regarded, how- 
ever, as venomous by the slaves, they are instantly 
killed or dreadfully mangled, and left to serve as food 
for racoons or for turkey-buzzards, ever on the watch. 
Sometimes they leave the soft mud in which they 
commonly burrow and take to the water, in which 
they swim with great swiftness. They are occasionally 
taken by persons angling for the common perch of 
Carolina {Pomotes vulgaris), with a bait of earth- 
worms. Sometimes they leave the water entirely, like 
eels, and are found on dry land ; but whether in search 
of food, or to rid themselves of parasitic animals, can- 
not at this moment be ascertained.” From its living 
in muddy places, it was called by the inhabitants the 
Mud Iguana. Its food is generally believed to con- 
sist of earth-worms, insects, &c. A specimen, which 
was kept alive in the Zoological Gardens, Eegent’s 
Park, in 1841, was supplied with about a dozen and a 
half of earth-worms daily. This individual was twenty 
inches long, and as large as the wrist of a stout child of 
six months old. Another specimen was kept alive by 
Dr. Patrick Neill, at Canonmills, near Edinburgh, for 
three or four years, and was made the subject of an 
elaborate memoir by the late Mr. James Wilson. 
During the whole of this period no change took place 
in its gills or lungs. Dr. Garden was the first person 
who discovered the Siren, and he sent an account of it 
to Linnaeus through our countryman John Ellis. These 
three naturalists, and the celebrated John Hunter, con- 
sidered it to be a perfect animal, and Linnaeus estab- 
lished a distinct order for it amongst the Amphibia, 
which he called Meantes. Pallas, Count Lacepede, 
and some others, considered it only a tadpole of some 
large species of Salamander ; and the celebrated ana- 
tomist Camper even went so far as to place it amongst 
the fishes. Cuvier, however, established most satis- 
factorily that the Siren was a perfect animal, and a 
true Amphibian, which respires at will throughout its 
life, either in the water by means of branchiae, or in 
the air by means of lungs. The blood-globules of the 
Siren were ascertained by Professor Owen to be, like 
those of the Proteus mentioned above, of a very large 
size ; and it appears now a well-established fact, that 
these globules are of a greater relative magnitude in 
the Perennibranchiate amphibians, or those which have 
persistent branchial apparatus, than in any other ani- 
mals of the class to which they belong. 
As we have mentioned, at p. 86, the order PsEU- 
DOiciiTHYAS will take its place in the article Fishes. 
END OF REPTILIA. 
