251 



CHAPTEE XVII 



THE GEOLOGICAL EANGE OF THE FOEAMINIFEEA 



In commencing a survey of the various foraminiferal 

 faunas of past ages we might naturally expect to 

 find the remains of such lowly organised and adapt- 

 able creatures as Foraminifera in great abundance in 

 the oldest fossiliferous rocks. But this does not 

 appear to be so, for the older Palaeozoic series has up 

 to the present yielded very few genera and species 

 of this type of animal life. At one or two horizons 

 only are their remains found in tolerable abun- 

 dance, and these are generally in the form of glau- 

 conite casts. On the other hand in these oldest 

 rocks certain examples have been found which have 

 the hyaline type of shell, and in which the original 

 structure has been wonderfully preserved. The 

 majority of the older Paleozoic Foraminifera have 

 been assigned to genera of the perforate type, such 

 as Lageiia, Nodosaria., Globigeriiia, and SjnriUina, 

 whilst in strata of later age in the same era the 

 arenaceous genera Hyj^eramnniiia, Stacheia, and 

 Textidaiia make their appearance. 



Seeing that the shells of the Foraminifera which 

 are as a rule so well preserved, especially in calca- 

 reous strata, as the limestones and calcareous shales, 



