EXPLANATION OF PLATE XVIII. 
Clepsysaurus Pennsylvanicus, Lea. 
1. A part of a Bone, probably of the Fore Arm or Leg. 
1 a. Transverse Section near the superior Part. 
1 b. Transverse Section of the inferior broken portion. 
1 c. Transverse section of the same at the middle. 
1 d. An oblique view of the superior fractured portion. 
2. An oblique view of a Centrum, with a portion of a second one. 
3. View of the Terminal Articular Cavity of a Centrum, broken on the left side. 
4. Vertical view of a broken Centrum, with a slight groove on its superior surface. 
5. Vertical view of three Centri, somewhat mutilated, in juxtaposition. 
