178 MR. D, M. S. WATSON ON 



Family Amphichelydid^. 



Broganochelys Baur. U. Trias, Wlirttemberg. 

 Proterocherys E. Fraas. „ ,, 



Super-Order SAUROPTERYGIA. 



Aquatic or semi-aquatic reptiles with a single temporal vacuity. 

 Neck long, the cervical rilps articulating solely with the centrum, 

 dox^sal ribs single-headed. 



A single coracoidal element. 



Pelvis with an obturator foramen. 



Sub-Oi'der Nothosavria. 



Semi-aquatic Sauropterygia. Paroccipital expanded and reach- 

 ing the squamosal, pterygoid, and quadrate so as to close the 

 middle ear behind. 



Radius and ulna, tibia and fibula long bones. 



JSfothosaurus Miinster. L. & M. Trias, Germany. 



Gymatosaurus Fritsch. M. Trias, Germany. 



etc. 



Sub-Order Placodonta. 



Sauropterygia with paroccipital not articulating with ptery- 

 goid and quadrate. Massive crushing teeth on the palatines. 

 (Body with a heavy armour of bony scutes.) Limb-bones long. 



Plaeodus Agassiz. M. Trias, Germany. 



Cyamodus „ ,, ,, 



Placochelys Jaekel. „ Hungary. 



Order Thalattosauria Merriam. 



Aquatic reptiles with a single lateral temporal vacuity. A 

 supratemporal present. A single coracoidal element. Occipital 

 region of skull unknown. Humerus twisted with expanded ends. 



7y^ , • ( ^6i'^i^^^- M- Trias, California and Nevada. 



Order Ichthyosauria. 



Aquatic reptiles with a single temporal vacuity, very large 

 orbits, and much elongated premaxillse. 



Basisphenoid without definite basipterygoid processes, ptery- 

 goids underlying much of its lower surface and that of the basi- 

 occipital. Neck short. 



Family Mixosaurid^. 



Ichthyosauria with relatively small orbits and short rostrum. 

 Upper end of the scapula expanded. Pubis and ischium broad. 



