152 REPTILIA class hi 



Order 2. SQUAMATA. (Lepidosauria, Streptostylica.) 1 



Body elongate, covered with corneous, or more rarely -with dermal sccdes or scutes. 

 Quadrate movably attached to the skull; the lower temporal arcade always, and upper 

 temporal arcade frequently wanting. Palatcd vacuities large, pterygoids not in contact 

 with vomer ; external nares separated ; teeth acroclont or pleurodont. Vertebrae well 

 ossified, usually procoelous, rarely amphicoelous ; sacral vertebrae not more than tvjo in 

 number. Post-cervical intercentra and abdominal ribs wanting ; dorsal ribs single- 

 headed. Limbs adapted for ambulation or natation, absent only among Ophidia and 

 a few Lacerfilia. 



This order comprises Lizards, Snakes, and two extinct groups of aquatic 



reptiles, — Dolichosauria and Pythonomorpha, — the earliest clearly recognised 



members of which occur in the Cretaceous. The Squamata are evidently very 



closely allied to Rhynchocephalians, and in all probability their origin is to be 



traced to that group. 



» 



Sub-Order 1. DOLICHOSAURIA. 



Small, aquatic, serpentiform reptiles, with well-developed lizard-like limbs and limb- 

 girdles. Vertebrae procoelous, and articulated both by zygapophyses and zygosphene- 

 zygantrum arrangement. Sacral vertebrae not anchylosed. Mandibles with sutural 

 symphysis. Teeth pleurodont. 



The family Dolichosauridae comprises a few genera from the English Chalk 

 and the Upper Cretaceous of Istria and Dalmatia, the largest of which^ attain 

 a length of between two and three metres. Dolichosaurus, Owen, has no less 

 than seventeen cervical vertebrae and large hollow ribs. Acteosaurus, Adrio- 

 saurus, Aigialosaurus, Ca.rsosaurus, Pontosaurus, and Mesoleptos are allied Istrian 

 genera. Most of the detached vertebrae of Cretaceous age, commonly classed 

 as Ophidian, are doubtless Dolichosaurian. Like the Pythonomorphs, these 

 forms probably passed away without leaving any post-Cretaceous descendants. 



Sub-Order 2. PYTHONOMORPHA. Cope.- 



Large marine reptiles with elongate body and two pairs of paddle-shaped appen- 

 dages. Skull lizard-like, elongate, depressed; superior temporal arcade and pineal 



1 Cope, E. D., Crocodiles, Lizards, and Snakes of North America (Ann. Rept. Smithsonian Inst., 

 1898), 1900. 



2 Literature : 



Baur, G., Morphology of the skull of the Mosasauridae (Journ. Morphol. vol. XII., No. 1), 1892. 

 — Cope, E. D., The Reptilian orders of Pythonomorpha and Streptosauria (Proc. Boston Soc. Nat. 

 Hist. vol. XII. p. 250), 1869. — The Vertebrata of the Cretaceous Formations of the West (Rept. 

 U.S. Geol. Surv. Territ. vol. II.), 1875.— Professor Owen on Pythonomorpha (Bull. U.S. Geol. Surv. 

 Territ. vol. IV. p. 299), 1878. — Cuvier, G., Sur le grand animal fossil de la craie de Maestricht 

 (Ann. Mus. d'Hist. Nat. vol. XII.), 1808. — DoIIo, L., Note sur l'osteologie des Mosasauridae (Bull. 

 Mus. Roy. d'Hist. Nat. Belg. vol. I.), 1882.— Ibid, vol. IV., 1885.— Nouvelle Note, etc. (Bull. Soc. 

 Belg. de Geol. Pal. et Hydrol. vols. III. -VII.), 1889-94.-6'^^, R. W., A Memoir on Mosasaurus, 

 etc. (Smithson. Contr. Knowl. vol. II.), 1864. — Goldfuss, A., Der Schadelbau des Mosasaurus (Nova 

 Acta Acad. Caes. Leop. Car. nat. cur. vol. XXL), 1843. — Leidy, J., Cretaceous Reptiles of the 

 United States (Smithson. Contrib. Knowl.), 1864. — Extinct Vertebrate Fauna of the Western Terri- 

 tories (Rept. U.S. Geol. Surv. Territ. vol. I.), 1873.— Marsh, 0. C, Characters of Mosasauroid 

 Reptiles (Amer. Journ. Sci. [3], vol. I.), 1871.— Ibid. vol. III. (1872) ; and XIX. (1880).— Merriam, 

 J. C, Die Pythonomorpha der Kansas Kreide (Palaeontogr. vol. XLL), 1894. — Osborn, H. F., A 

 complete Mosasaur Skeleton (Mem. Amer. Mus. Nat. Hist. vol. I. pt. 4), 1899. — Owen, R., On the 



