LACERTILIA. 335 



temporal arcade and resembles that of Varanus. It has an epipterygoid, 

 but resembles snakes and Rhynchocephalia in having a ligamentcus 

 symphysis to the lower jaw. Further there is a joint in each ramus just 

 behind its middle joint. Teeth are present on both jaws and on the ptery- 

 goids. The limbs a^e paddle-shaped ; they and their girdles are fairly 

 normal, but the long bones are much shortened and the digits often have 

 an increased number of phalanges and are without claws. There is no 

 clavicle, and the ilia are loosely, if at all, attached to the vertebral column. 

 They usually reach a considerable size (to 25 feet or more) and in their 

 general appearance recall that of the toothed whales. They are found 

 in the Upper Cretaceous of Europe, N. and S. America, and N. Zealand. 

 Mosasaurus Conyb. (Leiodon Owen), Upper Cretaceous of Maestricht 

 (Holland), of Belgium, France, X. Germany and N. America. Platecarpus 

 Cope, N. Amer. ; Clidastes Cope (Edestosaurus Marsh), N. Amer. ; Tylo- 

 saurus Marsh (Leiodon Cope), N. Amer. ; Hainosaurus Dollo, Belgium ; 

 Taniivhasaurus Hector, N. Zealand. 



Order 3. LACERTILIA * (AuTOSAuni). 



Reptiles with horny epidermal scales, moveable quadrate bones, 

 transverse anal opening, paired copulatory organs, a cloacal bladder, 

 and two sacral vertebrae. The skull is without a bony quadrato- 

 jugal arcade. 



The lizards always have an elongated and sometimes a snake- 

 like body. As a rule there are four limbs, which however scarcely 

 carry the body raised from the ground. In locomotion they are 

 used principally for pushing the body forward, but they may 

 also be used for clinging (Chamaeleon], climbing (geckos), and 

 digging. They usually end with five clawed digits. They are 

 sometimes so short and reduced, that they have the appearance 

 of stumps applied to a serpent-like body, and are without separate 

 digits (Chamaesaura}. In other cases vestiges of the posterior 

 limbs alone exist (Pseudopus, Pygopus, Fig. 183), or anterior 

 limbs alone are present (Chirotes], or finally external limbs may 

 be entirely absent (Anguis, Anelytropidae, Amphisbaena}. The 

 pectoral and pelvic girdles are however present, and in all lizards 

 except Amphisbaena there is at least a trace of the sternum, 



* Tiedemann, " Anatomic und Naturgeschichte der Drachen," Nurn- 

 berg, 1811. Wiegmann, " Herpetologica mexicana, Pars I, Saurorum 

 species amplectens," Berlin, 1834. Fischer, " Die Gehirnnerven der 

 Sauriern " Abh. a. d. Geb. der Naturw. Hamburg, vol. 2, 1852. Rathke 

 " Untersuchungen ueber die Aortenwurzeln u. die von ihnen ausgehenden 

 Arterien der Saurier," Denkschr. der Wiener Akad., 15, 1857. E. Schreiber, 

 " Herpetologica europaea," Braunschweig, 1875. G. A. Boulenger, 

 " Catalogue of the Lizards in the British Museum," London 1885, 3 vols. 

 E. D. Cope, " The Crocodilians, Lizards and Snakes of N. America," 

 Report of the U. S. National Museum, 1898, pp. 153-1,270, 1900. Huxley, 

 Zittel, Gadow, op. cit. 



