EMYS DECUSSATA.
trapezoidea; pectoralia transversa, quadrilatera, margine anteriore extrorsùm sinuata;
abdominalia magna quadrata, angulo postico-externo truncato, margine anteriore
curvo; femoralia et amlia trapezoidea; axillarìa anguste rhomboidea, anticè et
posticè acutè angulata ; inguinalia majora, triangularia, anticè acuta.
T esta ossea mensura.
unc. liti,
Longitudo d o r s i............................... 9 0
Latitudo ........................................................ 6 5
Longitudo s t e r n i ...................................................... 8 3
Altitudo........................................................................ 3 7
Amongst the Emydes of North America, the general similarity of which
renders it so difficult to distinguish the species by any tangible characters,—a
difficulty which is greatly increased by the numerous variations to which most
of them are subject,—the present species is one of the most striking, as offering
several characters readily appreciated, and sufficient to prevent it from being
for a moment mistaken for any other. Whilst in its general form, in the den-
tated outline of the posterior margin of the shell, in the character of its rugose
surface, and even in some of the lines and other markings both of the plates
and skin, it partakes of the same general character which belongs to Emys
reticulata, serrata, rugosa, irrigata, and ornata, it is at once distinguishable
from them all, by the absence of all regular pattern on the upper shell, the
uniform brown colour being interrupted only by a few spots of greater or less
intensity of the same hue, or, in young specimens, by a single pale mark on
each of the marginal plates. The rugose furrows of the plates are also characterized
by a more regular and marked decussation of the concentric and radiating
lines: the anterior vertebral plate is, quadrate, rather broader forwards,
whilst in all the others it is more or less panduriform or urceolate.
The pale yellow of the under side is marked, especially in young specimens,
by obsolete spots of a greyish brown colour, but so pale as to be only just
visible. Of these the most constant are found on the sutures of the marginal
plates, on the axillary and inguinal, and on the suture between the gular and
EMYS DECUSSATA.
humeral. In older individuals they entirely disappear, and the sternum sometimes
becomes irregularly clouded with brown.
Few species of the genus have been more frequently offered to me for
purchase than this; and it is strange that it should have remained so long
undescribed. I have possessed many of them living, and have had as good
an opportunity of observing their habits as the change of their condition
would permit. They are voracious, like their congeners, tearing in pieces and
greedily devouring meat, frogs, small fish, or any other food of this kind. On
being teazed, they snap at any object held near them with considerable quickness
and force. One of this species which I kept some years since, exhibited
a peculiarity in the manner in which it took its food, which does not appear
to belong to the species generally. On a portion of meat being presented to
it in the water, its fore legs were stretched out directly forwards, the palms
being placed outwards, and the feet were then agitated with a sort of vibratory
motion, during which the head was suddenly darted out to seize the prey.
I have not been able to ascertain from what part of America my specimens
were brought; but I have reason to conclude that they are found in various
parts of the United States.