1g2 FOSSIL TURTLES OF NORTH AMERICA. 
edge did not extend much below the triturating surface during life. We can not now tell 
how wide the triturating surface was originally. At its anterior end is seen a broad articular 
surface for the vomer. Cope thought that this surface was for the “‘zygomatic” bone. Cope 
did not recognize the suture between the lower and the upper portions of the mass of bone 
figured by him. The suture is not distinct, but the radiations on the surfaces of the bones 
show distinctly where the suture is located. The upper bone is the prefrontal, prj. On the 
inner side of its upper border is a broad articular surface for union partly with its fellow bone, 
partly with the frontal. Posteriorly the prefrontal articulated with the postfrontal, pops this 
excluding the frontal from the orbit. In Cope’s fig. 3a 1s seen a bridge of bone joining the 
prefrontal with the maxilla. The upper part of his bridge is undoubtedly the descending 
plate of the prefrontal which joined the vomer; the lower portion of the bridge is quite certainly 
a portion of the palatine. The foramen between the bridge and the maxilla is the nasopalatine. 
Cope did not explain the presence of such a bridge af bone on the supposed postfrontal. 
The bones described by Cope as the pterygoid and the columellar, and accepted as such 
by Baur, are the jugal, ju, and the quadratojugal, quj. Those of the right side are shown in 
Cope’ s fig. 5, plate x; those of the left side in his fig. 1, plate x1. What Cope regarded as the 
posterior send of the larger bone is the anterior. The more concave border formed a part of 
the rim of the orbit. The form of both these bones is almost exactly as in Archelon ischyros, 
as figured by Wieland. As in that species, the jugal extended backward to the quadrate. 
The hinder border of the quadratojugal is concave to form the anterior boundary of the 
tympanic cavity. | It is to be noted that the conspicuous oval mark shown in Cope’s fig. 1 
plate xi, is nothing but a little matrix overlaid by a thin layer of bone, probably of some fist 
In Cope’s fig. 5, plate x, the quadratojugal is in nearly i its natural position. It is there recog- 
nized as the zygomatic (quadratojugal), but it is the fellow of the bone which on the other 
side is determined as the ptery goid. The other bone, the jugal, has been turned end about, 
to agree with Cope’s idea of its proper position. 
Both quadrate bones are present; and that of the right side is represented in Cope’s 
fig. 5, plate x. Both are badly crusht, but that of the nght side shows the condyle less distorted. 
Just above the condyle, on the outside of the bone, is a scar where the quadratojugal articu- 
lated with the quadrate. On the inner border of the latter bone is another articular surface for 
the hinder end of the ptery goid. 
Cope’s fig. 2, plate xi, represents a bone which he identifies doubtfully with the anterior end 
of the ptery goid. It is really nearly the whole of the pterygoid, a small portion of the anterior 
end alone being broken away. Cope’s figure represents the bone as seen from below. At the 
hinder end of the bone, on its upper surface, is a large rough surface for articulation with the 
quadrate. From this extends forward a ridge which may have joined anteriorly either the 
columellar bone of the lower end or the descending process of the parietal. At the hinder end 
and below, and represented in Cope’s figure, is a rough excavation for the border of the basioc- 
cipital. The mesial half of the middle third of the lower surface is occupied by a rough surface 
which was overlapt by the basisphenoid. The relations here appear to have been muh as in 
Dermochelys. The pterygoids are relatively narrow, outer borders thickened and obtuse. 
The bone identified by Cope as the maxilla (fig. 247, sq) is the squamosal. Cope represents 
that of the left side. He regarded the curved order above the elongated process as the border 
of the orbit and states that the width of the bone below the orbit was 35 mm. Fortunately, the 
corresponding bone of the other side is present; and this shows that that curved border is the 
result of damage to the bone. The upper edge of the bone should extend above the lower 
border at least go mm. What Cope took to be the cutting-edge of the maxilla is the free, 
sharp, and smooth hinder border of the squamosal, ascending toward the parietal. What 
Cope regards as the premaxillary border is a free border descending to the quadrate. The wing 
of bone seen extending upward in Cope’s figures is the horizontal plate of the squamosal w hich 
OV erlapt the upper end of the quadrate and the outer end of the paroccipital. Pressure has 
caused it to lie nearly parallel with the body of the bone. On the outer border, that opposite 
the long, straight border, is seen a portion of the tympanic cavity. Wieland’s figure of the skull 
of this species shows that a process of the squamosal reaches the outer border of the parietal. 
The true postfrontal bone (fig. 247, pof) is present, but it was not figured by Cope and 
appears not to have been mentioned. It has on its lower border a process which articulates 
