STRATIGRAPHICAL PALEONTOLOGY 405 



VERTEBRATA : Fishes are of modern types ; many 

 Mesozoic types of Reptiles are extinct, only those 

 surviving which last to the Recent period (crocodiles, 

 turtles, lizards, snakes). Mammals are abundant, 

 mainly in freshwater deposits, and serve to some extent 

 as zone-fossils. 



PLANTS are of modern types, but many now confined 

 to warm climates (such as palms) are found fossil as far 

 north as the Arctic regions. 



SPECIAL FEATURES OF THE SEPARATE SYSTEMS. 



10. EOCENE. The foraminifer Nummulites is 

 very abundant, especially in the Middle Eocene. Ortho- 

 phragmina is confined to this system, except in America. 



The Echinoids Conoclypeus and Nucleolites survive from 

 the Cretaceous, but not beyond the Eocene. 



The same is the case with the Pycnodonts (GANOID 

 fishes). 



The Molluscan fauna of this period (in Britain and 

 elsewhere) resembles that now living in the Indian 

 Ocean. 



The Mammalia of the Lower Eocene are all small 

 and primitive, with forty four low-crowned teeth and 

 five-toed limbs. In the Middle and Upper Eocene they 

 rapidly become larger and more specialized. 



1 1. OLIGOCENE. The foraminifera Nummulites 

 and allied genera continue in some abundance. Lepido 

 cyclina replaces Orthophvagmina. 



The Irregular Echinoids Scutella and Clypeaster first 

 appear. 



Mammals. In Europe and America new families 

 appear, including the first (hornless) rhinoceros. In 

 Africa a distinct fauna was developing, including the early 

 ancestors of the elephant. 



12. MIOCENE. Nummulites is practically extinct. 

 Lepidocyclina persists at first, but is finally replaced by 

 Miogypsina. 



The Spatangids Micraster and Holaster, which have 



