162 KEPTILIA class in 



present in upper and lower jaws, and occur rarely on the palatines, pterygoids, 

 and vomer. They are either acutely or obtusely conical, chisel- or arrowhead- 

 shaped, serrated or carinated on the anterior and posterior edges, or in some 

 cases their form may be hemispherical. Their bases are completely fused 

 with the supporting bone, and their arrangement is either acrodont or pleuro- 

 dont. Successional teeth are developed on the inner side of the functional 

 ones, and gradually displace them. 



As a rule two pairs of limbs provided with five clawed digits are present, 

 although the hinder pair may be rudimentary, and in some cases both pairs 

 are wanting. The limb girdles persist, however, even among apodal forms, 

 but the pelvic arch may become reduced. The coracoid is relatively large, 

 and develops an anterior process, or precoracoid. The scapula also consists 

 of two portions, of which the distal (suprascapula) is the larger and usually 

 remains cartilaginous. The scapula proper is in some cases bifid at its distal 

 extremity. The rod-shaped clavicle connects the anterior border of the 

 scapula with the T-shaped or cruciform interclavicle, which is situated in 

 front of the sternum. The bones of the fore-limb resemble those of Rhyn- 

 chocephalians, except that the humerus never displays distal foramina. 

 There are eight small carpals arranged in two rows, and the usual phalangeal 

 formula is 2, 3, 4, 5, 3. 



Where the hind limb is normally developed, the ilia are movably attached 

 to the cartilaginous ends of the sacral ribs. Pubes and ischia meet in a 

 ventral symphysis, and the anterior border of the former frequently develops 

 a strongly curved process. The femur generally exceeds the humerus in 

 length, and the bones of the crus remain separate. The proximal tarsals 

 consist of a large tibiale (astragalus) and fibulare (calcaneum) ; there are 

 often but two free tarsals present in the distal row (Nos. III. and IV.), the 

 remainder being fused with the metatarsals. The phalangeal formula of the 

 pes is usually 2, 3, 4, 5, 4. 



Lizards of the present day are restricted almost exclusively to the tropical 

 and temperate zones, and according to Hoffmann they comprise 434 genera 

 and 1925 species. In comparison to these, the number of known fossil forms 

 is very insignificant. The oldest remains commonly associated with lizards 

 are the fragmentary jaws and procoelous vertebrae from the English Pur- 

 beckian, known as Macellodus brodiei, but these are too imperfect for accurate 

 determination. Most of the detached vertebrae and other fragments of 

 Cretaceous age which have been referred to Lacertilians or Ophidians are 

 probably Dolichosaurian. 



Even the known Tertiary fossils are very fragmentary, and belong for the 

 most part to existing families. From the Lower Eocene of Wyoming repre- 

 sentatives are known of the Varaniclae (Tinosaurus), Anguidae (Glyptosaurus, 

 Saniva, Xestops), Iguanidae (Iguanavus), and Chamaeleonidae. Iguana itself, 

 now restricted to the western hemisphere, occurs in the European Tertiary. 

 Fragmentary remains of a number of other recent genera are found in the 

 Eocene (or Oligocene) Phosphorites of Quercy, and Gypsum Beds of Apt, in 

 France, among which may be mentioned the following : — Proiguana (Fig. 255), 

 Plestiodofi (Fig. 256), Palaeovaranus (Fig. 257), Agama, Diploglossus, and 

 Lacerfa. 



The Miocene also yields a number of Lacertilian fragments identifiable 

 with recent genera, the principal localities being Auvergne, France ; the 



