THE PEE -ADAMITE EARTH. 



abounded, differing, however, both, in genera and species from 

 those which at present exist. Thus fossil Calamites, related to 

 the equisetum or mare's-tail, are found, which measure eighteen 

 inches in circumference and thirty or forty feet in height, while 

 the recent analogous species seldom exteeed an inch in diameter 

 and two feet in height. The fossil arborescent ferns called 

 Sigillaria, measure somefimes fifty feet in height, having their 

 summits covered with a splendid canopy of foliage. The foliage 

 of the herbaceous species is extremely elegant, presenting endless 

 varieties in their forms and in the skeletons of their leaves. The 

 fossil arborescent club-mosses, called Lepidodendra (from a Greek 

 compound signifying scaly tree), attain frequently an elevation of 

 from sixty to seventy feet. Some of these trees have been found 

 entire from their roots to their topmost branches. Their foliage 

 consisted of simple linear leaves, spirally arranged round the 

 stem. These leaves, in many cases, had been shed from the tree, 

 the marks of their points of attachment never having been 

 obliterated. In their external forms, the mode of ramification 

 and the disposition of their foliage, they closely resemble the 

 existing Lycopodiacese, or club-mosses. Notwithstanding the 

 enormous disparity of magnitude between these latter and the 

 fossil Lepidodendra, Brongniart has shown that both belong to 

 the same family. The fossils were in fact nothing more than 

 arborescent Lycopodiaceee, analogous in magnitude to the largest 

 existing pines, and forming extensive forests during the Car- 

 boniferous period, beneath whose shade flourished the lesser 

 ferns and associated plants now found with them in the same 

 coal strata. 



302. The contrast which such a flora presents with that 

 afforded by the woods and forests which now grow on the sur- 

 face of the carboniferous districts of England is as striking as the 

 discrepancy between the zoology of the Palaeozoic formation and 

 that of the present day. 



303. Among the Radiata of the Carboniferous period are enor- 

 mous quantities of corals denominated, according to their several 

 forms, tubipora, syringopora, catanepora, &c. Of the Echino- 

 dermata, crinoids swarmed in such infinite numbers that entire 

 strata are composed of their petrified remains. These species 

 have also received names indicative of their forms, such as 

 actinocrinus, cyathocrinus, and so on. 



Among the shells of the Carboniferous period are found innu- 

 merable Foraminifera, which are detected in slices of Yorkshire 

 limestone with the microscope. The upper strata of the moun- 

 tain limestone of the lower Yolga in Russia consist of masses of a 

 minute species of fusulina, resembling grains of wheat. Entire 

 58 



