334 CLASS REPTILIA. 



The remaining families are sometimes classed as Bhynchocephalia vera. 



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

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

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

 SiercostCDiuin Cope, Permian of Brazil. 



Champsosaurldae. Large aquatic reptiles with gavial-like head from 

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

 of Europe. Champsosaurus Cope. 



Rhynchosauridae. Skull massive with edentulous bent down beak-like 

 premaxillae ; upper jaw and palate with 3 or more rows of i^yramidal 

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

 Ht/perodapedon Huxley, 6 feet in length, no parietal foramen, Elgin Sand- 

 stones and Indian Trias. 



Sauranodontidae. Upper Jm-a of France. 



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

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

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

 without Tincinates, without intercentra in the dorsal region, without 

 entepicondylar foramen in the humerus. Upper Jurassic ; Ardeosaurus, 

 Acrosaurus v. Meyer ; Euposaurus Jourdan ; Pleurosaurus v. Mej^er ; 

 phenodon Grtiy {Hatteria Gray), living, N. Zealand. 



Sub-class 2. Leptdosauria (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 froximal 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 ; loiver jaw with 

 sutural symphysis. 



This order includes the long-necked Cretaceous form Dolichosaurus Owen 

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

 etc. probably belong to it. 



Order 2. Mosasauria.* 



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

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

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



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

 tinofuishable into cervical, thoracic, lumbar and caiidal. Zygosphenes 

 and zy2;antra are occasionally, but rarely, present. The skull has a superior 



* Sometimes called Pythonomorpha. 



