Case.] Turtles. 381 



as a fissure. The alar portion is small and not expanded. 

 Just opposite the stapedial fissure there is a small, but strong 

 articular surface for the petrosal. The superior end is very 

 broad and rough, and was probably overlain by the squamosal. 

 The borders of the alar portion show traces of sutural connection 

 with the quadrato-jugal throughout its length. The lower 

 articular surface is almost flat, somewhat constricted in the 

 middle portion, and looks a little forward as well as downward. 



The mandible is thus described by Cope : " The dentary bone 

 is stouter, but not as large as in T. latiremis, and is flattened 

 concave on its superior alveolar face, whose outer border, 

 though sharp, is not elevated above the level of the inner 

 border. The symphysis is short and there is no beak. The 

 inner face of the dentary is a broad, shallow groove." The 

 grooye on the inner side of the dentary is rather deep to be 

 described as broad and shallow. The symphysial portion is ex- 

 tended into a slight but unmistakable beak. 



The carapace was formed much as in the existing sea turtles. 

 The ribs are expanded, and suturally united for about their 

 proximal third on the anterior part of the carapace, and for 

 rather more than half of their length on the eighth and ninth. 

 The expanded portion contracts rapidly, leaving the slender 

 portion to join the peripherals. Proximally the expansion ex- 

 tends beyond the head of the rib and articulates closely with 

 the neurals, leaving no opening in the carapace in the middle. 

 The head of the rib extends well away from the flattened plate, 

 bending downward to articulate between the vertebrae. The 

 plates are suturally united with two neurals, the dividing suture 

 dividing the neurals meeting the rib plate at about its middle. 

 The proximal portion of the superior surface of the ribs shows 

 no sculpturing, other than a slight pitting, but, on the under 

 side, lines radiating from the origin of the head extend to the 

 distal end. Only the posterior part of the carapace is preserved, 

 showing five of the eight functional ribs, and the proximal part 

 of the tenth. The anterior of these are the longest, becoming 

 gradually shorter posteriorly, indicating a blunt, heart-shape 

 19— iv 



