109 



opposite the anterior part of the orbit. The latter presents only the anterior 

 and inferior outlines in the specimen. The part of the maxillary below it is 

 very narrow, and weaker than either Sphargis or Chelone. The cutting-edge 

 has a very open sigmoid flexure, the suborbital part being turned inward, the 

 anterior part a little outward. The osseous rim of the orbit projected out- 

 wards considerably beyond the plane of the maxillary anteriorly. 



The dentary hone is very deep anteriorly, and, like the maxillary, is a thin, 

 vertical lamina. The lower anterior angle is truncated by an acute, concave 

 margin. This is the anterior extremity of the symphysis. This suture 

 occupies the inner face of a triangular area, which extends but a short 

 distance on the lower margin of the ramus, and then passes upward and 

 backward for a short distance on the inner face of the ramus. That portion 

 above the symphysis diverges outward; thus producing a deep notch at the 

 symphysis, as though designed to receive a beaklike projection of the pre- 

 maxillaries. The cutting-edge has a slight sigmoid flexure, corresponding 

 with that of the maxillary ; it rises into a projecting angle. 



The posterior part of the ramus displays the cotylus, and, in front of it, 

 a deep, long fossa behind the articular bone. There is no angle nor coronoid 

 bone, as in all marine turtles. The superior margin of the dentary is thicker 

 posteriorly than in front; and its outer wall is produced backward as a thin 

 lamina, covering the surangular almost to the posterior edge of the ramus. 

 The angular is, as in recent forms, a narrow, wedge-shaped piece below the 

 dentary and surangular. The posterior edge of the surangular projects behind 

 the dentary, and exhibits an acute, convex edge rising forward. It supports 

 a small part of the articular cotylus on its inner face. Most of this portion 

 occupies the extremity of the articular. The latter sends a stout lamina 

 obliquely upward and forward to the lower posterior part of the dentary. 



The quadrate bones are of peculiar form. They exhibit the usual jJoste- 

 rior curvature above, with a shallow funnellike fossa for the tympanic cavity. 

 It presents two strong ridges anteriorly, an inner and an outer, which inclose 

 a deep, vertical concavity. The inner exhibits the suture with the pterygoid 

 bone; the outer, with the zygomatic. The superior border of the quadrate 

 within the squamosal is massive, and not inflated. Its surface is thickest 

 where the usual articulation with the opisthotic exists. The posterior hori- 

 zontal is short and deep. Tiie transverse part of the bone which support^ 

 inferiorly the exterior i)art of the condyle is thin, and disappears above to the 



