TESTUDINATA. 
63 
served that the widths of the dorsal scutes in the carapace No. 
7079, so far as they can be determined, are somewhat greater than 
in the one taken as the type. The lateral hinge-line is 26 mm. long 
and the bone is here only 4.5 mm. thick. 
The differences which the writer observes between the Pleis¬ 
tocene form and, the one with which it is compared are as follows: 
1. In T. major the greatest height of the shell is behind the 
middle of the length. From this point the outline descends rap¬ 
idly, backward. In T. innoxia the greatest height is at the middle 
of the length; and the descent is less rapid and is not much dif¬ 
ferent from the descent forward. 
2. In all the specimens of T. major at hand the nuchal bone 
is somewhat excavated in front for the neck. This is not usually 
the case in the fossil ; but in a fragment No. 7083, there is a slight 
curving inward of the border. 
3. In the existing species the nuchal scute is nearly or wholly 
suppressed. In the fossil it is well developed. 
4. In the existing species the hinder marginal scutes are uni¬ 
formly higher than they are in the fossil. The eleventh in No. 
29335 l 7 mni - high; in the fossil specimen 14 mim. high. 
The carapace numbered 7079 presents some features different 
from those of the one taken as the type. The median keel is want¬ 
ing. The hinder peripherals flare outward considerably, while in 
the type specimen they do so' hardly at all. In this respect, how¬ 
ever, similar differences are seen among the four specimens of T. 
major. Evidently the vertebral scutes of No. 7079 were broader 
than those of No. 7080, but here again similar differences are 
found among the specimens of T. major. The carapace of the 
fossil species is thin and light, excepting the peripheral bones. 
Above the bridge there is in the type carapace a hardly perceptible 
keel passing from the anterior free border to the hinder one; in No. 
7079 this is missing. This keel varies considerably among the 
four specimens of T. major. 
One fragment, No. 7083, of a carapace in which the bones had 
not become ankylosed presents the nuchal and the first peripheral 
of the left side. The nuchal is 30 mm. long, and 36 mm. wide. 
The thickness at the border which joins the first peripheral is 7 
mm. A fragment, No. 7084, comprises the bones on which lie 
the second, third, fourth, and a part of the fifth marginals. This 
