310 PALAEOZOIC TIME CARBONIFEROUS AGE. 



II. Life. 



1. Plants. 

 The land-vegetation of the Subcarboniferous period was very 

 similar to that of the Lower Carboniferous, and descriptions of spe- 

 cies are therefore not given in this place. It may have been as 

 profuse for the amount of land, although the circumstances were 

 less favorable for its growth and accumulation in marshes, — the 

 essential prerequisite for the formation of large beds of coal. 



2. Animals. 



The animal life was remarkable for the great profusion and 

 diversity of Crinoids, — or Sea-lilies, as they are sometimes called. 

 Some of the Crinoids — mutilated of their rays or arms, as is usual 

 with these fragile species — are represented in figs. 523-535. The 

 period might well be called the Crinoidal period in geological his- 

 tory. Among the kinds, the Pentremites (figs. 530-532) are perhaps 

 the most characteristic. Instead of having a circle of arms, like 

 most Crinoids, the summit is closed up so as to look like a bud 

 (whence the name Blastoidea, applied to the family, from the Greek 

 pXaarog, a bud), and the delicate jointed tentacles are arranged along 

 the pseudo-ambulacral areas in vertical lines. 



Among Corals, the auger-shaped Eetepores called Archimedes are 

 characteristic. (See fig. 537.) They are properly Molluscan of the 

 tribe of Bryozoans. A true Polyp-Coral, eminently characteristic 

 of the period, is the Lithostrotion Canadense (figs. 521, 522). It is a 

 columnar coral, having a conical elevation at the bottom of each of 

 the cells, and grows often to a very large size. 



Besides these, Brachiopods were numerous, especially of the 

 genera Spirifer and Productus. There were also many Cephalopods 

 of the genera Goniatites and Nautilus, and but few of the Orthoceras 

 family. Trilobites were rare ; Selachian and Ganoid fishes very 

 abundant. 



While the limestones of the West abound in fossils, the shales 

 and sandstones of the Appalachian region have afforded few of any 

 kind, and those mainly Conchifers and Gasteropods. ' 



The most interesting are the tracks of an amphibian reptile, — 

 Sauropus primcevus Lea, the earliest American species known. 

 Some of the tracks from near Pottsville, Pa., are represented on 

 fig. 549. There is a succession of six steps along a surface little 

 over five feet long: each step is a double one, as the hind-feet 

 tread nearly in the impressions of the fore--2et. The print of the 



