40S GEOLOGICAL SUCCESSION OF ANIMALS. 



of the family AsTEBiD2B the genera Stylina, Montlivaltia, 

 Thecosmilia, Rhabdophyllia, Cladophyllia, Goniocora, Isastrea, 

 Thamnastrea ; and of the family FUNGID^, the genera Como- 

 sfiris, Protoseris, are found in the Coral-rag of Wiltshire. 

 In the Great Oolite, besides species of many of these genera, 

 others belonging to Cyathophora, Convexastrea, Calamophyllia, 

 Cladophyllia, Clausastrea, occur. Similar coralbeds exist in the 

 limestones belonging to the Inferior Oolite, from whence the 

 genera Discocyathus, Trochocyathus, Axosmilia, Thecosmilia, 

 Latomeandra, Anabacia, with numerous species belonging to 

 many of the Coral-rag genera, are found. The echinoderms 

 present a great variety of forms. The crinoids are not quite 

 so numerous as in former ages. Among the most abundant 

 is the Pentacrinus. There are also comatula-like animals, 

 that is to say, free crinoids (Pterocoma pinnata). Many 

 star-fishes are likewise found in the various stages of this 

 formation. Finally, there is an extraordinary variety of 

 urchins, among them Cidaris and Hemicidaris (fig. 386, 7) 

 with large spines, and several other types not found before, as, 

 for example, Pygaster, Dysaster and Nucleolites (fig. 386, 3)] 

 677. The fauna of the Cretaceous period bears the same 

 general characters as the Oolitic, but with a more marked 

 tendency towards existing forms. Thus the Ichthyosauri 

 and Plesiosauri, characterizing the preceding epoch, are suc- 

 ceeded by gigantic lizards, approaching more nearly the rep- 

 tiles of the present day. Among the mollusca, a great num- 

 ber of new forms appear, especially among the cephalopoda, 

 as Ammonites, Crioceras, Scaphites, Ancyloceras, Hamites, 

 Baculites, Turrilites y some of which resemble the gasteropoda 

 in shape, but are nevertheless chambered. The Ammonites 

 themselves are quite as numerous as in the Oolitic period, and 

 are in general much ornamented. The acephala furnish us 

 also with peculiar types, not found elsewhere, as Magas, Ino- 

 ceramus, Hippurites, and peculiar Spondyli, with long spines. 

 There are also a great variety of gasteropoda, among which 

 some peculiar forms of Pleurotomaria, Rostellaria, and Ptero- 

 ceras y are very characteristic. The radiata are not inferior to 

 the other classes in the novelty and variety of their forms. 

 In figs. 387 and 388, some of the most characteristic fossil 

 shells from the lower greensand strata are represented. 



