CHAPTER IV 



SCALED REPTILES LIZARDS AND CHAMELEONS ORDER 

 SQUAMATA; SUBORDERS LACERTILIA AND RHIPTOGLOSSA 



ALTHOUGH in popular language the term lizard is applied to any four-legged 

 reptile, exclusive of turtles and crocodiles, in scientific usage it is more convenient 

 to restrict it to those members of the great group of scaled reptiles which do not 

 come under the designation of either chamseleons or serpents, whether they are 

 provided with legs, or whether they lack those useful appendages. Formerly, 

 indeed, lizards and chamaeleons were regarded as constituting an order by them- 

 selves quite apart from serpents, but the two groups are now known to be so 

 intimately connected as to render any such division inadmissible; and they are 

 accordingly here placed in a single order, known as scaled reptiles, or, technically, 

 Squamata. Structurally, thjs ordinal group differs very widely indeed from any of 

 those hitherto treated, and as it is essential to gain a correct idea of such structural 

 differences, they may first be taken into consideration. 



Taking their name from the coat of overlapping horny scales 

 with which they are generally invested, the scaled reptiles are 

 primarily distinguished from all the foregoing groups by the circumstance that the 

 quadrate bone is more or less movably articulated to the skull, and has its lower 

 end projecting freely therefrom, instead of being immov- 

 ably wedged in among the other bones. To this primary 

 point of distinction it may be added that the lower 

 temporal arch of the skull is wanting, so that there is 

 no bony bar . connecting the lower end of the quadrate 

 bone with the upper jaw, as there is in the crocodiles, 

 the absence of this bar being well shown in the figure of 

 a lizard's skeleton. Then, again, the palate, instead of 

 being more or less completely roofed over by bone, is 

 largely open, its bones taking the form of long bars. 

 In some lizards, as in the one of which the skeleton 

 is figured, the upper surface of the skull is covered 



I,EFT SIDE OF THE VERTEBRA 



by bone, so that the temporal fossae are roofed OF A SNAKE- 



over. 



Another important feature of the order is to be found in the circum- 

 stance that the ribs in the region of the back are single headed, and are 

 Vertebrae . 



articulated to the backbone by means of a facet (d) situated on the body 



of each vertebra. This feature at once distinguishes the order from the crocodiles and 

 dinosaurs, in which the ribs are two headed, and in the back articulate to a long 



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