BAENID. 89 
Nasals are present. The frontals are triangular, with one apex directed to the corre- 
sponding orbit, without reaching it. The exoccipitals meet in the midline neither above nor 
below the occipital foramen. The occipital condyle belongs wholly to the basioccipital. On 
the lower side of the skull the pterygoids exclude the quadrates from contact with the basioc- 
cipital and the basisphenoid. The latter bone does not quite reach the vomer. On each side 
Chisternon Chisternon 
hebratcum, undatum, 
No. 5961. No. 5962. 
Length from front of inaxilla to occip. condyle 67 72 
Width across the quadrates....... Danes 69 77 
Diameter of tympanic cavity..... oe ayers 16.5 21 
Breadth of temporal roof from orbit.......- : 24 29 
Diameter of orbit.......-..++. ees 20 2355 
Interorbital space........-.+++++-> ae : 20 23 
Breadth of maxilla below orbit.........----+- 8 13 
Width of pterygoids....... a mc eutenes 175 17.5 
Width of hinder end of maxilla from outside of 
cutting-edge to suture with palatine. .. . ‘ 11 15 
| Orbit to border of tympanic cavity. ...--...5055 18.5 25 
Width of pedicel of quadrates on level with palate 16 20 
of the basioccipital is a foramen, doubtless for a vein, wrongly regarded formerly by the 
author as for the internal carotid artery. 
The choane are placed far forward. There is no masticatory ridge on the maxilla. Just 
within the rim of the orbit there is a distinct suture which cuts off the lacrimal from the 
prefrontal. 
The lower jaw (fig. 81) presents a rather broad grinding surface. 
The femora of this specimen are present. The total length is 107 mm. The head is 
comprest. The plane passing through this head would come into contact with the tibial 
~I 
oo 
Fics. 78 AND 79.—Chisternon hebraicum. Skull. x2. No. 5961 A. M.N. H. 
78. Seen from above. fr, frontal; mx, maxilla; ma, nasal; pa, parietal; pro, prootic; sq, squamosal. 
79. Seen from below. ju, jugal; mx, maxilla; pal, palatine; pt, pterygoid; qu, quadrate; qu. art, articulation 
of lower jaw; Sy squamosal; vom, vomer. 
border of the distal end of the bone. In Trachemys elegans this plane makes an angle of 
re NG Aes Maat Salta see Signa = 
perhaps 40° with the axis of the bone on the tibial side. The diameter of the shaft of the femur 
of the species here described is 11 mm. The width of the distal end is 31 mm. 
No. 5904 of the American Museum was also found at Grizzly Buttes. It is believed to 
belong to the present species. It furnishes a large shell nearly complete, a portion of the skull 
and lower jaw, the neck, the shoulder-girdle, and the complete pelvis. The carapace has an 
axial length of 505 mm., anda maximum width of 470 mm. The carapace is moderately convex 
