212 THE OSTEOLOGY OF THE REPTILES 



IV. PARAPSIDA. A single temporal opening, between parietal and 

 postorbito-squamosal arch; supratemporal (tabular) persistent. 

 Ribs articulating more or less exclusively with centrum. A single 

 coracoid. 



8. Proganosauria. Skeleton largely primitive. Aquatic, the neck 

 and tail elongate. Phalangeal formula 2, 3, 4, 5, 4 (6). Skull im- 

 perfectly known; the quadrate fixed. Lower Permian. 



9, Ichthyosauria. Marine reptiles with short neck and all aquatic 

 adaptations. Vertebrae amphicoelous; no dorsal intercentra. 

 Quadrate fixed. Middle Triassic to Upper Cretaceous. 



10. Protorosauria. Aquatic or terrestrial. Not more than seven 

 cervical vertebrae. Vertebrae amphicoelous (PSaphaeosauridae). 

 Quadrate fixed. Phalangeal formula primitive. Lower Permian 

 to Jurassic. 



11. Squamata. Quadrate freely articulated proximally (strep- 

 tostylic) or secondarily fixed. 



A. Lacertilia {Sanria)} Parietals never united to basisphe- 

 noid by descending plates, the brain-case more or less mem- 

 branous anteriorly. 



(a) Kionocrania . An epipterygoid present-; vertebrae am- 

 phicoelous with persistent dorsal intercentra, or pro- 

 coelous and no dorsal intercentra; eight cervical verte- 

 brae; limbed or limbless. Phalangeal formula primitive. 

 Cretaceous to Recent. 



ijb) Platynota. An epipterygoid. Vertebrae procoelous. 

 Nine or more cervical vertebrae. Phalangeal formula 

 primitive. Lower Cretaceous to Recent. 



(c) Pythonomorpha. Marine reptiles; hmbs paddle-like, 

 hyperphalangic ; seven cervical vertebrae, procoelous; 

 an epipterygoid present. Upper Cretaceous. 



{d) Amphisbaenia. No epipterygoid or temporal arch, the 

 quadrate secondarily fixed; Hmbless or with vestigial 

 front legs; vertebrae procoelous. Oligocene to Recent. 



{e) Rhiptoglossa. No epipterygoid or clavicles^; five cer- 

 vical vertebrae; vertebrae procoelous; phalangeal for- 

 mula 2, 3, 4, 4, 3. Oligocene to Recent. 



B. Ophidia (Serpentes). Brain-case enclosed by descending 

 plates from parietals and frontals; no epipterygoids ; no 

 temporal arch; mandibles united by ligament. Vertebrae 

 procoelous, with zygosphenes; no chevrons. Limbless. 

 Cretaceous to Recent. 



V. DIAPSIDA. Two temporal openings, separated by postorbito- 

 squamosal arch; no supratemporals or tabulars (? Youngina). A 



^ [For a more comprehensive classification of the Lacertilia, see C. L. Camp, 1923, 

 Bulletin, Amer. Mus. Nat. Hist., XLViii, 289-481. — Ed.] 

 2 [Absent in Dibamidae. — G. K. N.] 

 ^ [Sometimes present, but small. — Ed.1 



