464 DISTRIBUTION IN SPACE AND TIME 



the last stage in the Palaeozoic epoch, formerly placed in the 

 Stegocephala, are now referred to an extinct order of Reptiles 

 (Proreptilia), which furnishes the nearest approach to the original 

 reptilian stock. A further stage in evolution was represented by 

 a second order (Rhynchocephala), from which the remaining 

 groups of reptiles have probably sprung. There is a single exist- 

 ing species, the Tuatara (Hatteria punctata] of New Zealand. 

 There were some other palaeozoic reptiles, but these will be 

 mentioned in dealing with the succeeding epoch. 



LIFE IN THE MESOZOIC EPOCH 



The animals of this 'epoch approached more nearly those of 

 the present day than did their palaeozoic predecessors. They 



included, however, a number of remark- 

 able extinct groups, some of which were 

 extremely dominant, while other classes, 

 e.g. Birds and Mammals, which now play 

 leading parts, were but feebly represented. 

 MESOZOIC ANIMALCULES (PROTOZOA). 

 The familiar chalk, which makes up the 

 Fig. i 3 ao.-Foraminifera from the " white cliffs of Albion ", and ranges east 



Chalk p _ . -i-ii 



far into Asia, was deposited in the later 



part of the epoch. It is very largely made up of the remains of 

 Foraminifera (fig. 1320), and before compacted and upheaved 

 must have borne a close resemblance to the foraminiferal oozes 

 which are now spread over a large part of the ocean floor. 



MESOZOIC SPONGES (PORIFERA). During the chalk period a 

 large number of Sponges possessed of siliceous skeletons existed 

 in the moderately deep sea, and it is their remains which chiefly 

 furnished material for the large flint nodules that abound in part 

 of the chalk, and which have a very particular interest for students 

 of the evolution of human civilization, since from them many of 

 the stone implements and weapons of prehistoric European races 

 were fashioned. 



MESOZOIC ZOOPHYTES (COZLENTERATA). Corals were extremely 

 abundant during the epoch, and many of them were reef-builders. 

 They belonged to the same great group (Hexactinia) that includes 

 the most typical recent forms, being, like them, distinguished by 

 a six-rayed symmetry. 



