334 CLASS REPTILTA. 



Tlie remaining families are sometimes classed as Rhynchocephalia vera. 



Mesosauridae. With numerous fine, briish-like teeth in the jaws ; neck 

 long, with short hatchet-shaped ribs ; tarsus with two bones in the proxuual 

 row. Permian and Trias. Mesosaurus Gervais, Lower Trias of S. Africa. 

 Ster coster num Cope, Permian of Brazil 



Champsosauridae. Large aquatic reptiles with gavial-like head from 

 the Cretaceous and Lower Eocene of N. Amer. and the Lower Eocene 

 of Europe. Champsosaurua Cope. 



Rhynchosauridae. Skull massive with edentulous bent down beak-like 

 premaxillae ; upper jaw and palate with 3 or more rows of pyramidal 

 teeth ; Trias. Rhynchosaurus Owen, Upper Trias, Warwickshire ; 

 Hyperodapedon Huxley, 6 feet in length, no parietal foramen, Elgin Sand- 

 stones and Indian Trias. 



Sauranodontidae. Upper Jura of France. 



Sphenodontidae- Upper Jura and present time. It is interesting to note 

 the long period (Cretaceous and Tertiary) in which these reptiles have not 

 been found. Homaeosaurus v. Meyer, very like Sphenodon, but ribs 

 without uncinates, without intercentra in the dorsal region, without 

 entepicondylar foramen in the humerus. Upper Jurassic ; Ardeosaurus, 

 Acrosaurus v. Meyer ; Euposaurus Jourdan ; Pleurosaurus v. Meyer ; 

 phenodon Gray (Hatteria Gray), living, N. Zealand. 



Sub-class 2. Lepidosauria (Squamata). 



With procoelous, rarely amphicoelous vertebrae, and with horny 

 scales ; sacrum of two vertebrae or absent ; ribs single-headed ; 

 abdominal ribs absent. Quadrate moveable, attached to the skull 

 by its 'proximal end only ; lower temporal arcade absent, palate 

 with many vacuities ; pterygoids not reaching to the vomers. 



The Lepidosauria comprise the orders Lacertilia and Ophidia 

 and the extinct groups of aquatic forms, the Dolichosauria and 

 the Mosasauria. 



Order 1. Dolichosauria. 



Small aquatic snake-like forms with well developed limbs and limb-girdles ; 

 vertebrae with zygantra and zygosphenes ; teeth pleurodont ; lower jaw with 

 sutural symphysis. 



This order includes the long-necked Cretaceous form Dolichosaurus Owen 

 with 17 cervical vertebrae ; and the genera Aigialosaurus, Pontosaurus, 

 etc. probably belong to it. 



Order 2. Mosasafria.* 



Large extinct marine reptiles, tvith two pairs of clawless five-toed limbs. 

 Skull varanus-like with a pineal foramen ; loiver jaw with ligamentous sym- 

 physis. Sacrum absent, the ilia not reaching the vertebral column. 



The vertebral column always contains more than 100 vertebrae, dis- 

 tinguishable into cervical, thoracic, lumbar and caudal. Zygosphenes 

 and zygantra are occasionally, but rarely, present. The skull has a superior 



* Sometimes called Pythonomorpha. 



