86 



THE FAR PAST. 



supposed that in strata so eminently marine, we are likely 

 to discover more than the merest indication of a terres- 

 trial vegetation. Still we can only reason from what we 

 know, and shape our inferences by the results of our ob- 

 servation. 



When we turn to the Fauna of the system, we find the 

 record much more complete and legible. We are presented 

 with infusorial organisms from its shales ; graptolites or ser- 

 tularian-like zoophytes in inconceivable numbers ; corals of 



SILURIAN HYDROZOA AND BRTOZOA. 



1. Oldhamia ; 2, Protcvtruiaria ; 3, Graptolites ; 4, 5, Diplograpsus 6, Didymograpsus ; 

 7, Rastriocs. 



many genera and species ; encrinites of various forms ; 

 star-fishes, independent and free-floating ; and sea-urchin- 

 like cystidece, attached to the sea-bottom by their jointed 

 foot-stalks. In molluscan life we have representatives of 

 every order brachiopods, acephalaiis, gasteropods, ptero- 

 pods, and cephalopods vegetable-feeders thronging the 

 shores, carnivorous orders in the open sea, and infusorial- 

 feeders in the deeper waters. The great preponderance of 

 brachiopods over acephalans and gasteropods is one of the 

 most noticeable features in the molluscan life of the period 

 a feature now reversed, seeing that acephalans and gas- 



