339 Tertiary Foraminifera 45 



The Foraminifera as a rule are not of pelagic habit. On the 

 contrary, by far the larger proportion, probably 98 or 99 per 

 cent, of the known recent "species" or "varieties," including 

 the whole of the porcellanous and arenaceous groups and the 

 bulk of the hyaline forms, inhabit the sand or mud of the sea 

 bottom, and are endow^ed with no swimming or floating powers. 

 This may be regarded as a well ascertained fa(5l. But on the 

 other hand, there are a certain number of forms belonging to 

 eight or perhaps nine genera, which it is equally certain pass 

 their existence, either in part or entirely at the surface of the 

 ocean or in mid-water. The pradlical importance of these com- 

 paratively few species is due to the extraordinary abundance in 

 which they are found, and the relatively large proportion of the 

 entire mass of the bottom deposit which is made up of their 

 shells. 



