II.] 



SPECIES AND SPACE. 



167 



of the same family, namely, Geotria chilensis}- is found 

 not only in South America and Australia, but in New 

 Zealand also. These fishes, however, probably pass part 

 of their lives in the sea. 



We thus certainly have several species which are com- 

 mon to the fresh waters of distant continents, although it 

 cannot be certainly affirmed that they are exclusively and 

 entirely fresh-water fishes throughout all their lives, except 

 in the case of Cfalaxias. 



Existing forms point to a close union between South 

 America and Africa on the one hand, and between South 

 America, Australia, Tasmania, and New Zealand on the 

 other ; but these unions were not synchronous any more 

 than the unions indicated between India and Australia, 

 China and Australia, China and North America, and India 

 and Africa. 



Pleurodont lizards are such as have the teeth attached 

 jy their sides to the inner surface of the jaw, in contra- 



INNER SIDE OF LOWER JAW OF PLEURODONT LIZARD. 



(Showing the teeth attached to the inner surface of its side.) 



distinction to acrodont lizards, which have the bases of 

 their teeth anchylosed to the summit of the margin of 

 the jaw. Now pleurodont iguaniaii lizards abound in the 

 South American region, but nowhere else, and are not as 

 yet known to inhabit any part of the present continent of 

 Africa. Yet pleurodont lizards, strange to say, are found in 



1 See Catalogue, vol. viii. p. 5U9. 



