AGE OF MOLLUSKS. 



195 



1. Oldhamia. 2. Protovirgularia. 3. Graptolites. 4, 5. Diplograpsus. 6. Did- 

 ymograpsus. 7. Rastrites. 



Fig. 102. 



frame-works of certain small animals called Hydrozoa 

 and Bryozoa, some of which contributed much to 'the 

 material for the formation of rocks in the Silurian age. 



285. Corals and Echinoderms. In Fig. 103 we have 

 specimens of these two divisions of the Radiates, which 



1. Heliolites. 

 6. Palaeaster. 



2. Catenipora. 3. Cyathophyllum. 4 Taxocrinus. 5. Cystidea. 

 Fig. 103. 



had so much to do with supplying the material for the 

 limestones in the age of Mollusks. One of the most 



