212 



FACTS AND FANCIES. 



tion from time to time of new groups, as if to 

 replace others which were in process of decay 

 and disappearance. 



Ill the later half of the Palaeozoic we find a 

 number of higher forms breaking upon us with 

 the same apparent suddenness as in the case of 

 the early Cambrian animals. Fishes appear, and 

 soon abound in a great variety of species, rep- 

 resenting types of no mean rank, but, singular- 

 ly enough, belonging, in many cases, to groups 

 now very rare ; while the commoner tribes of 

 modern fish do not appear. On the land, ba- 

 trachian* reptiles now abound, some of them 

 very high in the sub-class to which they be- 

 long. Scorpions, spiders, insects, and milli- 

 pedes appear, as well as land-snails, and this 

 not in one locality only, but over the whole 

 northern hemisphere. At the same time, the 

 land appears clothed with an exuberant vege- 

 tation — not of the lowest types nor of the 

 highest, but of intermediate forms, such as 

 those of the pines, the club-mosses, and the 

 ferns, all of which attained in those days to 

 magnitudes and numbers of species unsur- 

 passed, and in some cases unequalled, in the 

 modern world. Nor do they show any signs 

 of an unformed or imperfect state. Their 



