CXVlll INTIIODUCTION. 



Polyzoa for which I am indebted to Mr. A. Bell *. To 

 these must be added species detected by Manzoui in the 

 Italian Pliocene^ by Waters in that of Sicily, and by 

 E-euss in the Tertiaries of Austria and Hungary. Amongst 

 the latter are a number belonging to the Miocene age. 

 Altogether about 60 of our species have thus far been 

 recorded from the Tertiary beds. Two or three forms 

 seem to be identical with Cretaceous species. 



The Polyzoa are of venerable antiquity ; they occur 

 in the Palseozoic rocks, but are chiefly represented there 

 by the Cyclostomata \ or kindred forms. There is evi- 

 dence, however (as I learn on the excellent authority of 

 Mr. R. Etheridge^ Jun.), of the existence of a few Cheilo- 

 stomatous genera at least within this epoch ; and probably 

 the group is rej)resented in the Silurian division of it. 

 The Polyzoa abound in the Jurassic strata, and seem to 

 reach their maximum in the Chalk. In the latter the 

 Cyclostomata exhibit a wonderful variety and beauty ; tlie 

 Cheilostomata also have here reached their full deve- 

 lopment. 



Classification'. 



It is quite unnecessary to enter into the various systems 

 of classification which have long since had their day, and 

 which retain no permanent value. 



Johnston % recognized the Molluscan affinities of the 

 Polyzoa; and his classification in its leading features 



* lu tlie uomenclature adopted bj Mr. Bell the Middle Pliocene includes 

 the Coralline Crag and part of the Red Crag, and the Upper Pliocene such 

 portions of the latter as have a fauna closely assimilated to that of the 

 boreal European Seas. The term PalaoUthic is employed to designate 

 post-glacial deposits. 



t Of recent genera, Stomatopora and Diastopora appear to occur iu the 

 Silurian rocks. 



\ ' History of British Zoophytes,' 1847. 



