ERA OF THE 



cies of sea mollusks, of reptiles, and of mamm:fers 5 have 

 been changed again and again, since the cretaceous 

 era; and it is not till a long subsequent age that we 

 find the first traces of any other of even the humblest 

 species, which now exist ; but here have these humble 

 infusoria and polythalamia kept their place on earth 

 through all its revolutions since that time — are we to say 

 safe in their very htimility, which might adapt them to a 

 greater variety of circumstances than most other animals, 

 or are we required to look for some other explanation of 

 the phenomenon ? 



All the ordinary and more observable orders of the in- 

 habitants of the sea, except the cetacea, have been found 

 in the cretaceous formation — zoophytes, radiaria, mol- 

 lusks, Crustacea (in great variety of species,) and fishes in 

 smaller variety. In Europe, remains of the marine sau- 

 rians have been found; they may be presumed to have 

 become extinct in that part of the globe before this time, 

 their place and destructive office being perhaps supplied 

 by cartilaginous fishes, of which the teeth are found in 

 great ^quantities. In America, however, remains of the 

 plesiosaurus have been discovered in this part of the stra- 

 tified series. The reptiles, too, so numerous in the two 

 preceding periods, appear to have now much diminished 

 in numbers. One, entitled the mosaesaurus, seems to have 

 held an intermediate place between the monitor and 

 iguana, and to have been about twenty-five feet long, with 

 a tail calculated to assist it powerfully in swimming. Cro- 

 codiles and turtles existed, and amongst the fishes were 

 some of a saurian character. 



Fuci abounded in seas of this era. Confervae are found 

 enclosed in flints. Of terrestrial vegetation, as of terres 

 trial animals, the specimens in the European area are 

 comparatively rare, rendering it probable that there wai 

 no dry land near. The remains are chiefly of ferns, coni 

 fers, and cycadeee, but in the two former cases we hav< 

 only cones and leaves. There have been discovered man] 

 pieces of wood containing holes drilled by the teredo, an« 

 thus showing that they had been long drifted about in thi 

 ocean before being entombed at the bottom. 



The series in America corresponding to this, entitled 

 the ferruginous sand formation, presents fossils generally 

 identical with those of Europe, not excepting the frag 

 ments of drilled wood; showing that, j« this, as in earli 



