before the anterior extremity of the inguinal valves. The bones of the posterior
pairs are thickened over the point from which their median transverse connecting
rod diverges inwards. There is a considerable deposit of pigment in these localities,
in very young specimens, the whole of the area in the neighbourhood of the
second, third, and last pair of the plastral bones being deep black, this colour becoming
fainter with age; but it is still present in specimens measuring 4 inches in
length,
In animals 3 inches long, the anterior roughened surfaces are long. They
first make their appearance near the anterior extremities of the epiplastra, and
grow outwards as distinct plates beyond the external margins of the epiplastra, their
internal borders corresponding to the same border of the bones. The azygos
callosity appears on the arch of the entoplastron towards its posterior margin.
The lateral callosities first appear on the broad surface formed by the union of the
hyo-and hypoplastra, and extends as these bones grow on to the posterior rami
.of the hypoplastra, above the division, but less so on to their external rami, and
hardly reaching their internal rami. The hinder callosities, 0"-35 long in this
female, appear on the surface from which the three arms of each xiphiplastron
diverge, and gradually extend on to the first and hinder arms, but more so on to the
former on to the latter. These callosities do not extend on to the transverse
rami of the hypoplastral bones.
In examples 4 inches long, the plates of the epiplastra are more or less quadrangular,
separated from each other by two-thirds of their own diameters, while the
entoplastrai plate is a minute rough crescentic area. The hyo- and hypoplastral rough
surfaces have a straight anterior margin, two concave internal margins, one before
the other, and one external concave border. The xiphiplastra are rather elongated
ovals, separated from each other in their posterior halves by one-half of their
own diameters, their anterior halves being strongly divergent. In the fresh state all
these callosities are invested with a thin skin.
In the adult, the skin is thick and fleshy, the granules are round and pearly, and
on the inside of the sternum the callous plates are seen to invest the bones with
the exception of a short basal portion which permits the epiplastra to move freely
on the entoplastron. The development in the epiplastra is most extensive on their
posterior ends, the bony plate in that direction being more than twice the size of the
anterior section. The entoplastrai plate is developed downwards between the two
halves of the bone, the ends fit into the lateral plates before their anterior processes
and produce a notch in JE. punctata. The processes of the hyo- and hypoplastra
are wholly and broadly invested by the rough plates, only the extremities of their
internal processes remaining free in E. punctata. In adults, the xiphiplastral
plates embrace all their bones except their extremities anteriorly and posteriorly,
while three of the transverse processes fit into each other side by side, the tip of
each abutting against the opposite bony plate when the two halves of the plastron
are bent upwards and inwards, so that this motion is very limited, while motion
in the opposite direction is very free.
The outline of all the original bones and their processes can be detected in
the bony plates, so that it would appear that growth commencing in the parts
indicated in the young extends gradually in all directions, till at last this secondary
osseous structure embraces all the constituent bones, leaving only their articular
processes free, the bones themselves preserving their outlines.
Yariation, however, is not confined to the plastral plates, but occurs also in the
shells, independently of differences ascribable to age. In youth, the shell is of a
more rounded form than in after life, when it is a more 'elongated oval. In some
specimens the anterior margin of the shell and the anterior vertebral swelling
are fuller than in others; the vertebral line is raised in a few, while in others it is
rounded off at the sides.
In fresh healthy specimens, the upper shell is always entirely covered with
skin so thick as to obscure the granular surface under it, but in adults it sometimes
becomes abraded, exposing the almost white granular shell below it.
These curious mud turtles when left to themselves will slowly and cautiously
extend their necks, but as soon as they are approached they do not attempt to
escape, but withdraw with great rapidity into their shells and firmly close them. I
have never observed them snap at objects, in the same way as Trionyx, and the
much more formidable Chitra, which darts out its long neck with a rapidity unparalleled
among animal motions.
When the head is retracted it is completely hidden so that the anterior margins
of the carapace and sternum meet. The skin on the long retracted neck forms
two folds; the innermost but highest fold is so formed that its upper border, which
is slightly longer than the snout, and so, doubtless for the protection of that sensitive
part, overhangs it j but at the sides of the mouth it slopes downwards and backwards,
the free margin in that position of the fold lying along the chin, so that by
this arrangement the mouth is not covered by this fold. The most external fold
which is formed by the skin at the base of the neck, covers the whole of the inner
fold against which it lies, and all that part of the mouth left uncovered by it, leaving
only the nostrils unprotected.
The neck when retracted is so doubled on itself, that the base of the cervical
vertebrae, at the anterior extremity of the carapace, is on the same line with the
tip of the snout, the posterior bend being opposite the inguinal notch of the
sternum, and pushing backwards before it the coils of the intestines which partially
embrace it on either side.
This, like the other members of the genus, frequents muddy bottoms, and, when
jheels dry, it buries itself in the mud, at no great depth below the surface.
The female in laying her eggs, which are round and about an inch in diameter,
scrapes a shallow hole for them in the mud and then covers them up.
They are exclusively vegetable and grain-feeders.
This species appears to be generally distributed throughout Burma, extending
along the various rivers that debouch into the main stream, from Lower Pegu up
to Bham6, where I obtained examples, and it doubtless ranges still higher.
c 5