BEYOZOA OR POLYZOA. 



121 



of Fenestella and Synocladia, another Cryptostome, are G-allery 

 mounted on blocks. VIII. 



The next fauna represented in England is that of the Case A6, 

 Jurassic system. This shows a great advance on that of ^^^^ 

 the Palaeozoic ; old types such as Fenestella, Penniretepora, 

 Acantliocladia disappear, and species belonging to existing 

 genera form the larger part of the fauna. Among these the 

 Cyclostomes, Stomatojoora, Berenicea, and Diastopora are 

 important, and are illustrated by an extensive series of 

 specimens, but Theonoa and Apsendesia are typically Jurassic. 

 These are associated with forms such as Ceriopora, which 

 are survivals of the Trepostomata. 



The ensuing Cretaceous fauna in many ways resembles ^^^^ 

 the Jurassic. Trepostomata survive, and the Cyclostomata ^ast Sides, 

 are still in the ascendant. Examination, however, of the 

 specimens exhibited shows that the Cheilostomata are now 

 fairly abundant, as we may see by the numerous species of 

 Membranipora and Onychocella (Fig. 65) and the presence of 

 more specialised genera such as Crihrilina. 



Passing to the Eocene we find that the fauna in England ^^^^^^^ 

 became smaller, thougrh that of the Mediterranean Basin at ^ ®* 



the same period was very large. The forms, moreover, were 

 scarce and dwarfed, as they lived in a sea exposed to the 

 north and cut off from the warm waters of the Mediterranean 

 by a land barrier across Central France and Germany. 

 Hence in our series genera such as Idmonea are represented 

 only by small delicate colonies (see also Idmonea coronopus, 

 from the Paris Basin), which are in striking contrast to the 

 massive growths exhibited from Italy. In addition to these 

 general differences, the fauna includes a high percentage of 

 peculiar species, among which Orbitulipora petiolus, consisting 

 of a disc supported on a short stem (see specimen B. 4349), 

 Adeonellopsis Wetherelli, and Notamia Wetherelli, are the 

 most remarkable. The species of the still existing genera 

 Schizoporella, Smittia, and Entalopliora, on the other hand, 

 are quite modern in form. Except for the Cyclostomes 

 Idmonea and Entalopliora, all the genera mentioned in this 

 paragraph are Cheilostomes. 



The Pliocene in England is much richer than the Case A5, 

 Eocene, and comparison need only be made between the "^^^^ 

 small fragile specimens from the latter and such massive 

 colonies as those from the Crags, to realise that the Bryozoa Wall-case 

 were then living under more favourable conditions ; the 

 Arctic Ocean was probably cut off by a land barrier to the 



