404 PAL/EONTOLOGY 



The last British Trigonia is found in the Cenomanian 

 (Middle Cretaceous.) 



Ammonoidea and Belemnoidea become gradually 

 less abundant and finally die out. More or less uncoiled 

 Ammonoids are common. 



In certain regions (especially North Africa, Syria, 

 South America, and the southern U.S.A.) there are 

 Upper Cretaceous Ammonoids with suture-lines closely 

 resembling those of the Triassic Ceratites (pseudo- 

 ceratites). 



In the Upper Cretaceous there is a sudden appearance 

 of Fishes and land-plants (Dicotyledons) of much 

 more modern types than those of the Jurassic and Lower 

 Cretaceous. 



ZONE-FOSSILS. Ammonites and Belemnites, supple- 

 mented by Brachiopods and Echinoids in Northern 

 Europe, by Rudistes and Foraminifera in the Mediter- 

 ranean province. 



IV. GENERAL FEATURES OF THE 

 CAINOZOIC FAUNAS. 



Foraminifera are abundant and include forms of 

 much greater size than in most earlier systems. These, 

 where they occur (mainly in tropical and sub-tropical 

 regions), are the best zone-fossils. 



Corals are not abundant except in warm latitudes. 



Crinoids and Brachiopods are rare. 



Echinoids are common, especially in warm latitudes, 

 where two new families abound : the flat Scutellids and 

 the flat or pyramidal Clypeastrids. Spatangids increase in 

 abundance. 



Lamellibranchs and Gastropods are extremely 

 abundant, and include many new families. Their 

 species have too long a range to serve as zone-fossils, 

 but the age of a bed can often be fixed exactly by the 

 association of several species, some of which range 

 upwards and others downwards. 



CEPHALOPODA are rare, Ammonoids and typical 

 Belemnoids being extinct. 



