STRATIGRAPHICAL PALAEONTOLOGY 401 



SPECIAL FEATURES OF THE SEPARATE SYSTEMS. 



4. DEVONIAN. BRACHIOPODS: of horny Inarticu- 

 lata, only Lingula and Discinids (Oybiculoidea) survive 

 (lasting to the Recent period). Terebratuloids first appear, 

 but are not common. Most other Silurian families 

 survive. Spire-bearers abound. 



Goniatites are common, with very simple suture- 

 lines ; they serve as zone-fossils. 



TRILOBITES : much reduced in numbers, but the same 

 families as in the Silurian except Illo'iiids and Encrinurids. 



FISHES very abundant, especially Ostracoderms and 

 Ganoids. 



LAND-PLANTS (PTERIDOSPERMS, etc.) not very common. 



5. CARBONIFEROUS. Blastoids commoner 



than in any other system. 



BRACHIOPODS : Productus, Spirifer, and Rhynclwnel- 

 lids most abundant. Terebratnlids fairly abundant. 



CEPHALOPODA : Goniatites with suture-lines a little 

 more complex than in Devonian ; tightly-coiled NAUTI- 

 LOIDS. 



TRILOBITES rare, of only one family (Proetida). 



VERTEBRATA : fish- teeth and spines common in some 

 beds. OSTRACODERMS are extinct. AMPHIBIA in Coal 

 Measures, rare. 



PLANTS abundant in the coal-bearing beds. In the 

 northern hemisphere (except India) the fern-like leaves 

 of Pteridosperms, and stems of Lepidodendron, 

 Sigillaria and Calamites are common. In India and 

 the southern hemisphere, there is a totally distinct flora 

 (Permo-Carboniferous), with the fern like Glossopteris. 



The zoning of the Lower Carboniferous is based on 

 shallow- water Corals and Brachiopods, and the zones may 

 be of restricted geographical extent (pp. 392-3). The 

 Upper Carboniferous (Coal Measures) are classified, but 

 scarcely zoned, by the flora : their marine equivalents by 

 Goniatites, as are the marine Permian. 



6. PERMIAN. The true marine fauna is only 

 known in a few restricted (tropical and sub-tropical) 



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