458 DISTRIBUTION IN SPACE AND TIME 



sufficiently bulky volume in which to study the evolutionary his- 

 tory (phylogeny) of animal groups. As will be seen from the 

 above indication of the types dominant in the successive epochs, 

 there has been a successive progress from low to high, in con- 

 formity with the doctrine of evolution; but the record is very 

 imperfect, and that part of it belonging to the Eozoic is made 

 up of pages which so far have turned out to be practically blank. 

 Many parts of the world, however, are ^.s yet unexplored, so far 

 as their geology is concerned, and during the last few decades 

 the additions to our knowledge have been so great that much is 

 to be hoped for in the future. 



LIFE IN THE PALEOZOIC EPOCH 



That animal life existed long before the commencement of this 

 epoch is sufficiently shown that in its earliest stage all the great 

 groups of Backboneless Animals (Invertebrata), save those en- 

 tirely devoid of hard parts capable of preservation, are represented, 

 mostly by forms which we are able to classify with some approach 

 to certainty. And before the epoch came to an end all the classes 

 of Backboned Animals (Vertebrata), except Primitive Vertebrates 

 (of the past history of which, owing to the soft nature of their 

 bodies, we can never hope to learn much), Birds, and Mammals, 

 had come into existence, as testified by numerous fossils. 



PALEOZOIC ANIMALCULES (PROTOZOA). The Ray-Animalcules 

 (Radio larid] and Forams (Foraminifera) are here and there abun- 

 dant. The flinty shells of the former make up hard siliceous 

 bands (cherts) which were certainly deposited in very deep water, 

 and correspond to the Radiolarian oozes which now cover parts of 

 the ocean floor. Some of the limestones (e.g. the Fusulina lime- 

 stone) belonging to that part of the epoch when our coal-fields 

 were formed are made up mainly of the shells of Foraminifera, 

 and these may be compared to the wide-spread foraminiferal oozes 

 of the present day. 



It may be remarked, in passing, that some of the rocks of the 

 Eozoic epoch (in Brittany) contain the remains of Ray-Animal- 

 cules. 



PALEOZOIC ZOOPHYTES (CCELENTERATA). The variously-shaped 

 colonial forms known as Graptolites (Rhabdophora, fig. 1313) are 

 largely represented in some of the older Palaeozoic rocks, and the 



