362 REPTILIA. 



attached behind to a movable quadrate bone, which is in turn 

 connected with a movable squamosal, this giving an enormous 

 width of gape to these animals. In the Lizards, however, even 

 in those most like the Snakes, the halves of the lower jaw are 

 firmly united to one another in front, and though the quadrate 

 bone is usually more or less movable, the jaws can in no case 

 be separated to anything like the extent that characterises the 

 Ophidia. 



The Lizards are distinguished from the Crocodiles, amongst 

 other characters, by the fact that the integumentary covering is 

 in the form of horny scales, never with bony " scutes," whilst 

 the teeth are rarely or never sunk into distinct sockets. In many 

 cases the teeth are anchylosed to the summit of the margin of 

 the jaw ("acrodont" dentition); in other cases they are at- 

 tached by their sides to the inner surface of the jaw (" pleuro- 

 dont" dentition). 



The whole order of the Lacertilia is very often united with 

 the next group of the Crocodilia, under the name of Sauria. 

 The term " Saurian," however, is an exceedingly convenient 

 one to designate all the reptiles which approach the typical 

 Lizards in external configuration, whatever their exact nature 

 may be ; and from this point of view it is often very useful as 

 applied to many fossil forms, the structure of which is only im- 

 perfectly known. It is therefore perhaps best to employ this 

 term merely in a loose general sense. 



It is hardly possible, with our present knowledge, to speak 

 very positively as to the exact range of the Lacertilia in time. 

 This uncertainty arises from two causes firstly, that there is 

 some doubt as to the exact age of some deposits which have 

 yielded Lacertilian remains ; and secondly, that the affinities of 

 some extinct Reptiles are a matter of considerable question. 

 Upon the whole, the oldest known Lacertilian would appear to 

 be the Protorosaurus of the Middle Permian Rocks ; though 

 good authorities have placed this form in the Crocodilian group 

 of the Thecodontia. Protorosaurus attained a length of between 

 three and four feet, and differs from all existing Lizards in 

 having its teeth implanted in distinct sockets this being a 

 Crocodilian character. In other respects, the Permian reptile 

 approximates closely to the living Monitors ( Vdranidie), and its 

 slightly-cupped vertebrae would lead to the belief that it was 

 aquatic in its habits. 



In rocks known, or supposed, to be of Triassic age, nume- 

 rous Lacertilian reptiles have been discovered, of which the 

 most important are Telerpeton, Hyperodapedon, and Rhyneho- 

 saurus. Telerpeton occurs in strata near Elgin, in Scotland, 



