THE PENNSYLVANIAN PERIOD 



173 



to building up certain Pennsylvanian limestones in America, 

 Europe, and other continents. 



Porifers. — Sponges were present but they require no special 

 mention. 



Coelenterates. — Among these the Corals only have left 

 records, and even these do not appear to have been abundant. In 



Fig. 101 



A Permo-Carboniferous landscape, showing some of the most conspicuous 

 plants of the great Coal Age. Lepidodendrons (with branches) and Sigil- 

 larians (without branches) in the left background; Equisetae (segmented) 

 on the right; Seed-ferns in the left foreground; two Amphibians (Eryops) 

 on the land; a primitive Reptile (Limnoscelis) in the water; and a great 

 Insect (Dragon-fly) in the air. (From a drawing by Prof. S. W. Williston.) 



eastern North America and western Europe the physical geography 

 conditions were distinctly unfavorable to them. 



Echinoderms. — Of the Pelmatozoans (stemmed Echinoderms) 

 only the Blastoids and Crinoids remained, the former having 

 become extinct during the period. The Crinoids showed a remark- 



