ONE-CELLED ANIMALS OR PROTOZOA 47 



flinty. The diagram (Fig. 8) shows some fossil 

 shells of Protozoa from the marl of Barbadoes. 

 These constitute a deposit which was named " In- 

 fusorial earth," in the earlier days of microscopic 

 observation, when all Protozoans were spoken of 

 as Infusoria. The name, Infusoria, it must be 



FlG. 8. Fossil Skeletons of Polycystina, from the so-called 

 " Infusorial Earth " of Barbadoes, highly magnified. 



recollected, is now restricted to a special class, to 

 which the forms in question do not belong. 

 These fossil forms were named Polycystina, and 

 are still often spoken of under that name, al- 

 though the animals that present the peculiar fea- 

 ture of possessing " more than one cyst " now are 

 4 



