EMYS DECUSSATA. 
trapezoidea; pectoralia transversa, quadrilatera, margine anteriore extrorsum sinuata; 
abdominalia magna quadrata, angulo postico-externo truncato, margine anteriore 
curvo; femoralia et analia trapezoidea; axillaria anguste rhomboidea, antice et 
postice acute angulata; inguinalia majora, triangularia, antice acuta. 
Testee osseae mensura . 
unc. lin. 
Longitudo dorsi. 9 0 
Latitudo . 6 5 
Longitudo sterni. 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 charac¬ 
terized by a more regular and marked decussation of the concentric and radi¬ 
ating 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 
