74 STORY OF THE REPTILES 



thing further. Besides these there were once many 

 forms, now extinct, the peculiarities of some of which 

 will be referred to as we go along. 



Limbs 



The limbs of the reptiles v.re rather like those of 

 the amphibians in a general way, except that the 

 claws are well developed. The webs of the toes are 

 not so noticeable, though tlie tortoises, crocodiles, 

 and tuatera have swimming membranes. All rep- 

 tiles swim well, however, and the tortoise-forms, 

 crocodiles, and some snakes are especially aquatic. 

 Many fingers and toes, rather than few, prevail gen- 

 erally, though there are some remarkable exceptions. 

 The number of toes may run from one to five. Xor- 

 mally there are five before and five behind, but where 

 the limbs tend to be lost, the toes decrease also, till in 

 a certain skink-like lizard there is only one toe be- 

 hind, and in some greaved lizards there is only one 

 finfi^er in front. 



In the sea-tortoises the toes are all massed into 

 paddles which are often much like fins, except that 

 thev have the three divisions of the les', a characteris- 

 tic of all quadrupeds ; and in some ancient forms {3Io- 

 sasaiirs and Iclithyosaurs) the limbs were still more 

 fused and flattened. In the fossil IcJdhyo^aurs^ some 

 species were found which had six, possibly seven, rows 

 of bones inside the paddles. It seems probable, in 

 one case, that the two outside rows were merely extra 

 bones on each side of the original five fingers for they 

 are not joined to the hard bones properly ; but in an- 



