283 



This conclusion of the identity with living types of many 

 of the Infusorial forms, which occur in tertiary and supra- 

 tertiary deposits, is in harmony with researches into other 

 tribes of fossil animals. But, in extending our view to 

 older strata, some difference arises in this respect. It is 

 well known that at the most, only one or two species 

 of the fossil shells which occur in the chalk are identical 

 with recent shells ; and there is no other tribe of the 

 animal kingdom, except the microscopic races, which yield 

 even one such analogue, in the chalk or strata below. But 

 of the microscopic Infusoria, Ehrenberg mentions three living 

 species which occur in the flint, viz. : — 



Peridinium pyrophorum. 

 Xanthidium ramosum. 

 „ hirsutum. 



And three others, which occur in the white chalk, viz. : — 



Fragilaria rhabdosoma. 



„ striolata. 

 Gaillonella aurichalcea. 



He also enumerates in the white chalk of England, 

 Denmark, and Sicily, nine species of Foraminifera, which 

 are also living in the sea, viz. : — 



1. Globigerina bulloides. 



2. „ helicina. 



3. Rosalina globularis. 



4. Rotalia ocellata. 



5. globulosa. 



6. „ perforata. 



7. „ turgida. 



8. Textilaria aciculata. 



9. „ globulosa. 



If we reflect on the number of the fossil forms here 

 referred to living types, the great skill and patience of 

 the observer, and the support which he has received to a 

 certain extent from other naturalists, we shall be disposed 



