200 STRUCTURE OF NUMMULITES. 



grey marble of Derbyshire is, indeed, an entire mass 

 of marine productions. 



Most remarkable is it that such mountain masses of the 

 remains of a single family of shells should be added to the 

 solid materials of the globe. But it should not be for- 

 gotten, that each individual shell had once a place within 

 the body of a living animal, and that then the waters of 

 the ocean which covered Europe were filled with float- 

 ing swarms of these beings which are now extinct. The 

 Clio borealis, referred to in page 147? is now so nume- 

 rous in the Northern Ocean, that in calm weather the 

 surface of the water swarms with such millions of them, 

 rising for a moment to the air at the surface, and again 

 instantly sinking towards the bottom, that the whales 

 can scarcely open their huge mouths without- gulping 

 in thousands of them ; yet the nummulites must have 

 rivalled them in number. 



These creatures are divided into air chambers, which 

 act as a float, but the last cham-ber is not sufficiently 

 large to contain any part of the body of the animal. 

 The chambers are very numerous, but they have no 

 siphon. In each species of this genus the essential 

 parts vary in form, but the principles of their structure 

 and operation appear in all to have been the same. 



If, however, these animal bodies have contributed to 



