402 MANUAL OF ZOOLOGY. 



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 

 imperfectly known. It is therefore perhaps best to employ 

 this term merely in a loose general sense. 



The Lacertilia are often divided into the two great groups of 

 the Fissilinguia and Brevilinguia, according as the tongue is 

 bifid and protrusible like that of the Ophidians, or is thick and 

 fleshy, and only protrusible when the mouth is open. These 

 distinctions, however, are not of any very great value, and 

 no good general arrangement of the order has hitherto been 

 proposed. Here, therefore, it will be sufficient to treat very 

 shortly of the more important families of the Lacertilians. 



The first family of any importance is that of the Chalcida or 

 Chalcidi-an Lizards,, comprising a number of snake-like animals 

 which have long occupied a debatable position. In their ser- 

 pentiform cylindrical form these animals closely resemble the 

 true Ophidia, and this likeness is still further increased by the 

 absence or rudimentary condition of the limbs. The scapular 

 arch and sternum, however, are present in a rudimentary form, 

 and one or both pairs of limbs may be present. Another 

 character, separating the Chalchice from the true snakes is the 

 structure of the lower jaw, the rami of which are united in 

 front by a symphysis so as greatly to restrict the gape. The 

 Chalcidian Lizards are entirely covered with similar scales 

 arranged in rings or whorls ; the trunk passes into the tail 

 without any definite line of demarcation, and there is generally 

 a lateral longitudinal fold or groove; In Chalddes the body 

 is long and snake-like, but all the limbs are present, though 

 these are small,, and may have but a single well-developed toe 

 each. It is represented in both the East Indies and South 

 America. In Chirotes> r of Mexico, only the fore-limbs are 

 present, and in the African genus Bipes only the hind-limbs are 

 present. In the Amphisbana of South America the tail is 

 very short,, and the vent is placed nearly at the end of the 

 body, whilst there are no limbs. In the Glass Snake (Ophi- 

 saurus} of the United States there are also- no limbs. 



The next great family is that of the Scincida, including a 

 number of small Lacertilians, some of which are completely 

 snake-like, whilst others possess two limbs, and others again 

 have the normal two pairs of limbs in a well-developed condi- 

 tion. All possess movable eyelids, and in all the conforma- 

 tion of the lower jaw is Lacertilian, and not Ophidian. All 

 the Scincoidean Lizards have the body covered by similar 

 scales overlapping one another like the scales of fishes, whilst 



