LACERTILIA AND CROCODILIA. 437 



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 pro- 

 posed. 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 tlie Chakidce or 

 Chalcidian 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 Ofhidia, and this likeness is still further increased by the 

 absence or rudimentary condition of the limbs. The scapular 

 arch and ^ernum, however, are present in a rudimentary form, 

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

 character separating the Chalcida 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 Chalcides the body 

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

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

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

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

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

 present. In the Amphisbmnm 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 Scincidce, including a 

 number of small Lacertilians, some of which are completely 

 snake-Hke, 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 

 the head is protected by larger plates. The tongue is free, 

 fleshy, and slightly notched. Of the snake -like forms of 

 this group, none is more familiarly known than the Blind- 

 worm or Slow -worm {Aiignis fragilis, fig. 170), which is 

 found over almost the whole of Europe, in western Asia, 

 and northern Africa, and which is one of the most abun- 

 dant of the British Reptiles. The Blind-wonn possesses no 



