228 ANCIENT TYPES OF SOUTHERN HEMISPHERE. [CH. V 



majority are in the most southern parts of the globe; 

 New Zealand itself had quite recently a number of species 

 as great as all the existing forms. The northern types of 

 birds, for instance the sandpipers, crows and hosts of 

 others, embrace no forms that can be regarded with any 

 probability as more ancient than the Ostrich tribe. 

 Among Reptiles the Hatteria, allied to the triassic 

 Hyperodapedon, has been driven quite to the verge of 

 inhabitable country ; it has even got beyond New Zealand 

 to a few small islands off the coast. Turning to another 

 group of animals, the Dipnoid fish exemplify what has 

 been said in a forcible way; the three existing genera 

 Geratodus, Protopterus and Lepidosiren are confined 

 respectively to Australia, South America, and certain 

 parts of Tropical Africa. The fossil remains of Dipnoi 

 are common in the more ancient strata of this country 

 and of North America. Even invertebrates fall in with 

 the theory to some extent. It seems on all grounds 

 reasonable to conclude that the genus Lumbricus, and 

 its immediate allies, are the most modern existing forms ; 

 these genera are precisely those which are indigenous to 

 the northern hemisphere only, where they form, with 

 a few exceptions, the only earthworms met with. 

 The more archaic Perichaetidse, Acanthodrilidse and 

 Cryptodrilidae are characteristic of the southern hemi- 

 sphere while the Acanthodrilidse which are very possibly 

 the oldest existing family of the group are particularly 

 antarctic in their range. The fresh water Crayfishes fall 

 in with the other groups cited; and the facts in their 

 distribution and structure agree entirely with those of 



