PALEOZOIC ROCKS AND ERA. 275 



(Figs. 170, 171), to show their general appearance. They 

 belong to the lowest order of plants. 



Animals. 



These are far more numerous and diversified than the 

 plants. We can mention only such as may be recognized 

 even by the untrained eye. 



Corals. These are very abundant, and seem some- 

 times to have formed veritable reefs. There are three 

 very characteristic forms, viz., 6^-corals (Cyathophyl- 

 loids, Figs. 172, 173), Honey com ^-corals (Favositids, Fig. 

 174), and Cftatw-corals (Halysitids, Fig. 175). These 



FIG. 173. 



FIG. 172. 



FIGS. 172, 173. Cyathophylloid corals : 172. Lonsdaleia llorif ormis. (After Nichol- 

 son.) 173. Strombodes pentagouus. (After Hall.) 



are all characteristic of the Paleozoic, and the last char- 

 acteristic of the Silurian. Now, any one can recognize 

 these, especially the Honeycomb and Chain corals, and 

 therefore when these arc found any one may identify 

 Paleozoic or even Silurian rocks. 



Hyclrozoa. In still, sheltered bays, with fine imid- 

 bottom, are now found, attached to sticks, logs, or sin -Us, 

 fine, feathery things, which look like finely dissected sea- 

 weed or sea-moss. They are, indeed, gathered by ama- 



