PREHISTORIC ANIMALS 



421 



Palaeohatteria, of the order Rhynchocephalia, which has a single 

 genus, Hatteria(Fig. 396), existing to-day. The most interesting 



reptiles, however, belong to two orders now- 

 extinct, the Theromorpha (Gr. Oi]p, beast, and 

 fxopcf)i), form) and the Sauropterygia (Gr. aavpos, 

 lizard, and irTepv^, wing). The former were 

 lizardlikc, with appendages adapted to walking 

 on land; they are confined to the rocks ol the 

 Permian and Triassic, and have been found in 

 Africa, Europe, and North America. The latter 

 were also lizardlike, some small but others very 

 large ; they attained their greatest development 

 in the Mesozoic era, so we may defer a descrip- 

 tion of them for the present. An interesting 

 genus of the Dipnoi appears here, Ceratodus 

 (Fig. 397). which still exists in Australia; it is 

 the only genus of Palaeozoic vertebrates which 

 has persisted through all the succeeding geologi- 

 cal periods to the present time. 



These five periods, from the Cambrian to the 

 Permian inclusive, constitute the Palaeozoic group 

 or era, so called because the vast majority of the 

 animals living then were very different from those 

 at present inhabiting the earth ; they have almost 



V 



Fig. 398. Lingula, 

 one of the oldest 

 Brachiopoda; nat- 

 ural size. (Drawn 

 from specimen.) 



Fig. 399. Echinosphce- 

 rites aurantium, one of 

 the Cystoidea ; fossil. 

 ( Drawn from specimen 

 by the author.) 



too. Granato- 

 ennus, one of the 

 Blastoidea; fossil. 

 ( I )rawn from speci- 

 men by the author.) 



entirely become extinct, leaving no descendants. In some cases 

 there may be only a single living representative of a group that 

 at this early time was very abundant. Thus, the only living genus 



