. Carnegie Institution of Washington publication. FOSSIL TURTLES OF NORTH AMERICA. On the lower surface of the skull (fig. 688) are to be noted the broad triturating surfaces of the maxilla?, each presenting about the same relative amount of surface as in P. ferox. 1 he transition between the triturating surface and the cutting-border ot the jaw is rather abrupt. The choanal fossa is likewise formed somewhat abruptly. In the midline in front of the choanae may be seen the suture where the inner borders of the maxillae meet below the vomer. A portion of the vomer is exposed in front of this
. Carnegie Institution of Washington publication. FOSSIL TURTLES OF NORTH AMERICA. On the lower surface of the skull (fig. 688) are to be noted the broad triturating surfaces of the maxilla?, each presenting about the same relative amount of surface as in P. ferox. 1 he transition between the triturating surface and the cutting-border ot the jaw is rather abrupt. The choanal fossa is likewise formed somewhat abruptly. In the midline in front of the choanae may be seen the suture where the inner borders of the maxillae meet below the vomer. A portion of the vomer is exposed in front of this suture. The anterior palatine foramen is small, only ~ mm. long, while in the specimen of P. ferox referred to above, it is u mm. Figs. 687-689.—Atnyda? tritor. Skull of type. X i- \ ' ' 1] 6S8. View of lower surface. 689. View of right side. I he choanae arc relatively small, being constricted as in Amyda cartilagtnea and A. sinensis, and the constriction has been produced in the same manner in the fossil, as in living species. I he basioccipital bone is rather broad, occupying nearly one-third of the width of the posterioi pan oi the mot ol the mouth, the lateral portions being formed by the pterygoids. This region is slightly concave both transversely and longitudinally. The articular surface of the quadrate is 20 mm. wide, from side to side, being relatively greater than in the case of P. ], rox. 1 he squamosal processes, formed by the backward extension of the squamosal and the paroccipiral bones, are large and Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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