148 Transactions of the Society. 



disappear at the end of the Silurian period. Dictyonema, a doubtful 

 Graptolite, extends from the Cambrian to the Devonian. 



III. CCELENTERATA :— II. Anthozoa. 



Of the Cokals, the Eugose and Tabulate corals are confined to 

 he Palaeozoic rocks. 



The Hcxacoralla are first seen in the Trias and continue to the 

 present day. Zaphrentis, Petraia, Clisiophyllum and Strcphodcs, 

 all simple types of Eugose corals, range from the Silurian to the 

 Carboniferous age. 



The same range is found for Cyathophyttum and Dvphyphyllum, 

 both of which are compound forms. 



Of the Hcxacoralla, four genera range from Jurassic to Eecent. 



Of the Tabulate corals (among the Eugosa), Farosites and 

 Syringopora range from Silurian to Carboniferous times. 



The existing corals belong to the Madreporaria, the Fongida, 

 and Perforata, and have no palaeozoic representatives, but the 

 Secondary and Tertiary deposits have yielded a large number of 

 these forms. The composite Madrepora include a vast number of 

 forms and range from the Eocene to the present day. 



IV. ECHIXODEEMA. 



Of the Echinoderma, the extinct groups the Cystoids and 

 Blastoids only lived in the Palaeozoic period. 



Of Cystoids, 50 genera and 250 species are known, and 



Of Blastoids, 19 genera and 120 species are recorded. 



The Crinoids appear to have declined ever since their maximum 

 development in Palaeozoic times. 



Ichthyocrinus ranges from the Ordovician to the Carboniferous. 



Taxocrinus has the same range. 



Of later forms, Pentacrimis, Extracrinus, and Antcdon have 

 persisted from the beginning of the Mesozoic period with very little 

 •change. 



Starfishes range from the Cambrian to the present day. 



Echinoids : regular forms like Cidaris have existed since the 

 Trias. 



Echinocorys and some other irregular forms appear in the Creta- 

 ceous, but many of the genera quickly became extinct. But both 

 regular and irregular forms have continued on to the present time. 



V. POLYZOA ("Sea-Mats"). 



The Polyzoa date back to the Ordovician. 

 Of Cyclostomata, Stromatopora and Berenicea range through 

 the whole time to Ordovician. 



