THE SUBCLASS DIAPSIDA 279 



A. SUPERORDER DIAPTOSAURIA 



Teeth on some or all the palatal bones, acrodont or protacrodont. 

 No antorbital opening; no interparietals or tabulars. Vertebrae 

 amphicoelous. Dorsal ribs holocephalous, articulating in part or 

 chiefly to centrum. Two or three sacral vertebrae. Fifth tarsale 

 absent. Phalangeal formula never reduced. Parasternal ribs 

 present. 



In the absence of more complete information as to the structural 

 details of some of the forms included under this group name, and in 

 the differences of opinion, as usual, as to the value of the groups, 

 the tribe or superorder Diaptosauria has a present use. Several 

 groups formerly placed under it are now relegated to other divisions. 



14. ORDER RHYNCHOCEPHALIA 



Terrestrial or littoral lizard-like reptiles of small or moderate size. 

 Palate primitive, with teeth on some or all the bones. Pectoral 

 girdle complete. Dorsal ribs holocephalous, articulating in inter- 

 central space and arch. 



The three groups of reptiles here considered suborders are by 

 some authors given a family rank, by others ordinal. Except the 

 living Sphenodon, most of the genera are yet incompletely known. 

 The differences between them seem hardly greater than among the 

 Lacertilia with the inclusion of the Pythonomorpha. 



A. Suborder rhynchosauria 



Skull more or less depressed and broad, with a strong, decurved, 

 and edentulous beak, formed by the premaxillae. Temporal open- 

 ings relatively large, their boundaries as in the Sphenodontia. No 

 parietal foramen. Nares undivided. Palate with small interptery- 

 goidal opening. Dorsal intercentra absent or unknown. About 

 seven or eight cervicals and twenty- three presacrals; two sacrals. 

 A small pubo-ischiatic vacuity. Humerus without epicondylar 

 foramina. 



A small group of terrestrial, perhaps in some cases subaquatic, 

 shore-dwelling and shell-eating reptiles from three to six feet in 

 length. The complete skull, tail, and mesopodials are known in 

 none. In Howesia a distinct intermedium tarsus is figured ; if not an 



