192 HORN EXPRDITION 8VMMARY. 



The lizards of tlie south-east part of tlio eoiitinnut do not form in any way a 

 distinctive group and are represented partly hy forms widely distril)uted over the 

 whole continent, partly by eastern eoast.al species, partly l)y western and southern, 

 hut with the exception of Physignathus, they do not contain a representative of 

 the distinctly northern group. 



Talcen altogether Australia does not show any markcfl aiHnity in tlie matter 

 of lizards with any other region, its exotic genera having prol)al)ly entered hy the 

 nor(Ji-east and thei'e is little or no :i,IIinity with .South America,. Speaking of the 

 distrihution of lizards Wallace says,* "on the whole the distribution of the Lacer- 

 tilia shows a remarkable amount of specialization in each of the great tropical 

 regions, whence we may infer that Southern Asia, Tropical Africa, Australia and 

 South America each oiitained their original stock of this order at very remote 

 periods, and that there has since l)een very little intercommunication between 

 them." The absence of any marked atlinity between Australia and other regions 

 in the Lacertilian fauna stands in marked contrast to that of other orders, but in 

 connection with this it may be pointed out that the climate of any Antarctic land 

 connection, though temperate enough to suit mammals, may not have Ijeen favour- 

 able to the migration of such heat-loving creatures as lizards. It may indeed be 

 said that we iind an alliance existing between Australia and South America 

 amongst tiie groups in the case of wiiich we nnglit have expected to do so if that 

 alliance be due to a connection across a moderately cool Antarctic land. 



Amphibia. — In the Amphibia one family, the Cystignathida', is common to 

 Australia and South America. Out of fifteen genera no fewer than twelve are 

 endemic. Rana is represented by one species in the Cape York peninsula, and this 

 genus together with Hyla may be regarded as an innnigrant from the north. The 

 stionghold of the endemic genera is undoubtedly the eastern and southeastern 

 coastal ilistrict and though some of the more widely dispersed species may perhaps 

 represent foi'ms once more widely distributed but now separated by the gradual 

 desiccation of the intei'ior, others doubtlessly owe their wide dispersal to the 

 remarkable power which they possess of accounnodating themselves l)y burrowing 

 and storing up water to districts which they can only traverse during irregularly 

 recui'ring rainy seasons. 



Pisces. — Amongst fresh-water fishes the more important forms are : — 



(1). Ceratodu.s, the remnant of a more widely dispersed form, now confined to 

 the Mary and Burnet Rivers in Queensland, though fossil remains found in the 



* Distribution of Anim.ils. Vol. II., p. 404. 



