174 HISTORICAL PALAEONTOLOGY. 



which attained such a striking prominence in the Secondary 

 period, probably commenced its existence during the Coal 

 period' but these anticipatory forms are comparatively few in 

 number, and for the most part of somewhat dubious affinities. 



CHAPTER XIII. 



THE CARBONIFEROUS PERIOD Continued. 

 ANIMAL LIFE OF THE CARBONIFEROUS. 



We have seen that there exists a great difference as to the 

 mode of origin of the Carboniferous sediments, some being 

 purely marine, whilst others are terrestrial ; and others, again, 

 have been formed in inland swamps and morasses, or in brack- 

 ish-water lagoons, creeks, or estuaries. A corresponding dif- 

 ference exists necessarily in the animal remains of these de- 

 posits, and in many regions this difference is extremely well 

 marked and striking. The great marine limestones which 

 characterize the lower portion of the Carboniferous series in 

 Britain, Europe, and the eastern portion of America, and the 

 calcareous beds which are found high up in the Carboniferous 

 in the western States of America, may, and do, often contain 

 the remains of drifted plants; but they are essentially charac- 

 terized by marine fossils; and moreover, they can be demon- 

 strated b} the microscope to be almost wholly composed of 

 the remains of animals which formerly inhabited the ocean. 

 On the other hand, the animal remains of the beds accompany- 

 ing the coal are typically the remains of air-breathing, terres- 

 trial, amphibious, or aerial animals, together with those which 

 inhabit fresh or brackish waters. Marine fossils may be .found 

 in the Coal-measures, but they are invariably confined to spe- 

 cial horizons in the strata, and they indicate temporary depres- 

 sions of the land beneath the sea. Whilst the distinction here 

 mentioned is one which cannot fail to strike the observer, it is 

 convenient to consider the animal life of the Carboniferous as 

 a whole : and it is simply necessary, in so doing, to remember 



