PROTOZOA. FORAMIXIFERA 27 



largely of their shells, as for instance, the Saccammina- 

 limestone of the north of England and Scotland, the 

 Endoth ^ra-limestone of North America, and the Fusulina- 

 limestone of Russia, China, Japan and North America. 

 The Foraminifera are mostly of small size in the Permian 

 of England ; they are comparatively rare in the Trias, but 

 become abundant in the Jurassic, where, however, rock- 

 building types are generally absent. In the Lias the 

 introduction of numerous vitreous species {Nodosaria, 

 Cristellaria etc.), many of which appear to be allied to 

 forms now living in tropical or warm-temperate regions 

 only, is noteworthy ; some porcellanous forms belonging to 

 the Miliola group are also fairly common. A larger number 

 of genera and species are found in the Middle and Upper 

 Jurassic than in the Lias. 



The Order continues to be well represented in the 

 Cretaceous formations, particularly in the Gault and 

 Chalk — Orbitolina, Ccdcarina, Globigerina, Rotalia etc. 

 being common. Some beds of the Chalk, especially the 

 Micraster zones and the Chalk Rock, are largely composed 

 of Foraminifera such as Globigerina, Textularia, Bolivina, 

 Flabellina. 



The Foraminifera attain their greatest development 

 in Tertiary and recent times. In the Eocene deposits 

 Niimmulites is often extremely abundant and of large size, 

 forming the greater part of the massive Nummulitic 

 Limestone of Southern Europe, Egypt, Asia Minor, and 

 the Himalayas ; Miliola, Orbitolites, Alveolina, Operculina, 

 and Orbitoides are also important rock-building forms in 

 the Eocene period. In the English Eocene, Foraminifera 

 are numerous in the Thanet Sands and the London 

 Clay ; in the Barton and Bracklesham Beds Niimmulites, 

 Miliolina, Alveolina etc. occur. Amphistegina is abundant 



