EXPLANATION OF PLATE XVII. 



Superior cranial walls of Pythonomorplia, from below and above, one-half natural size. 



Fig. 1. Clidastes iortor, from below. 



2. Platecarpus curlirostris, from below. 



3. Platecarpus ictericus, from below. 



4. Platecarpus ictericus, from above. 



5. Platccarjyus mudgei, from below. 



6. Platecarpus corypliaus, from below. 



7. Clidastes stenops, from below, without prefrontal bone. 



8. Clidastes stenops, from above, with right prefrontal bone. 



