PLEUROSTERNID&. 51 
These intergulars slightly overlap the entoplastron. The humero-pectoral sulcus passes 
behind the entoplastron. Dr. Baur’s figure of the median sulcus represents it as running an 
exceedingly irregular course. In fig. 19 this sulcus is probably represented much too straight. 
On the bridges are very distinct inframarginals, as represented in fig. 19. Only the angles 
of these extend over on the peripheral bones. 
Dr. Baur states that a nuchal scute is present in this species, but in No. 336 it can not 
be distinguisht with certainty. On most of the peripherals the sulci may be seen, both on 
the upper and the lower sides. The boundaries of the three anterior vertebrals have been 
determined quite satisfactorily. The width of these scutes is about 90 mm. 
Dr. Baur has briefly described the shoulder-girdle. This is present in specimen No. 336 
(figs. 20, 21) altho the distal portions of the coracoids are damaged so that their exact form 
can not be determined. The left half of the girdle is least injured and distorted. Here we 
find the scapula, the procoracoid process, and the coracoid standing at nearly right angles with 
one another. In this respect they are much as in Chelydra. The scapula is relatively shorter 
than in Chelydra, and the procoracoid is shorter still. “The lower end of the scapula is strongly 
comprest. The glenoid fossa is removed outward some distance from the perpendicular 
portion of the scapula. This fossa presents some interesting peculiarities. It measures 7 mm. 
by 9 mm. and it has the long axis directed nearly horizontally. The fossa of Chelydra, nearly 
of the same shape, is directed nearly perpendicularly. Furthermore, there is, running along 
near the lower border of the fossa, a prominent ridge, which is found to correspond to a groove 
on the head of the humerus. Nothing of the kind is found in either Chelydra or Testudo, 
except in the most rudimentary form. However, in a specimen of Trachemys rugosa there are 
found similar structures; but here too, the long axis of the fossa is directed strongly upward. 
Examination of the naturally articulated parts of Trachemys shows that the motion of the 
humerus is nearly confined to a plane which is directed backward and downward. The 
motion of the humerus of a TJ estudo, with its round head, is much more free and varied. The 
T estudo is a tortoise adapted solely for walking; the Trachemys is to a great extent a swimmer. 
Dr. Baur states that the fore limb of Compsemys (Glyptops) is long and resembles the 
elements of the Emydidae. However, the humerus (fig. 22) is a little shorter proportionally 
than in Trachemys rugosa and the limb is rather feeble. The humerus is but little more than 
one-half as long proportionally as that of Chelydra. The bone is, however, not so slender 
as that of Trachemys, but has more of the form and proportions of Chelydra. This applies 
also to the size of the radial and ulnar tuberosities. The distal end of the humerus has points 
of interest. Its breadth is like that of Chelydra. There is distinct evidence of the presence 
of a deep coronoid depression. The ectepicondylar foramen pierces the bone at a distance 
of 11 mm. above the condyle. The trochlear surface reminds one of that of some mammal. 
Instead of forming an elongated smooth surface, convex in both directions, it presents two 
prominent ridges separated by a groove. ‘The distal end of the humerus of Trachemys rugosa 
presents a somewhat similar structure, but the guiding ridges are far less prominent. As in 
Glyptops, the most prominent one is that for the head of the radius. The result of these 
arrangements must be that the motion of the forearm of both genera is confined to one plane, 
like that of the forearm of a man. 
There is this difference, however, between the humeri of Trachemys and Glyptops. In 
the former these ridges run nearly parallel with a plane passing through the long axis of the 
head of the humerus. The effect of this is to make the forearm move in the same plane as 
the upper arm; that is, downward and backward. In Glyptops, on the other hand, the ridges 
of the trochlear surface are directed at an angle of about 45° with the plane of the head of the 
humerus. Hence, when the limb is drawn backward, the humerus moves in a horizontal 
plane, while the forearm, if flext, would move downward and backward. 
One ulna is present. It is slightly longer proportionally to the humerus than it is in 
Trachemys, and its distal end is broader. Of the hand the writer can say nothing. 
Baur has dealt with the pelvis without figuring it. He errs with regard to the inner ramus 
of the pubis, when he says it is a slender element and that the ischium is larger than the pubis. 
The contrary is true (figs. 23, 24). The pubis, aside from the lateral processes, does not differ 
greatly from that of Chelydra or Testudo. In the specimen before me it has an antero-posterior 
extent of at least 25 mm. It is quite deeply notcht in front. Baur is possibly, but not certainly 
