170 SHELLS AND MOLLUSCOUS ANIMALS. 



mysterious process, the mollusk derived from the 

 materials forming his food: materials which in 

 themselves possess scarcely any portion of this 

 substance, and yet which, when mingled with 

 animal matter, serve to compose the calcareous 

 habitation : and those towering chalk cliffs on which 

 the short grass is now growing, or that long stra- 

 tum of limestone, extending for miles away, is 

 formed almost entirely of shells mingled with the 

 skeletons of zoophytes and sea urchins, and other 

 marine animals. The block of marble, hard as it 

 seems, reveals, by the aid of a microscope, masses 

 of shells, some of them perfect and unbroken, and 

 rivalling in symmetry the loveliest shell in the 

 cabinet of the collectors : while the myriads of 

 shells lying in crushed heaps among the mountains, 

 are hourly undergoing those processes by which 

 they shall, after the lapse of ages, form the com- 

 ponent parts of the gem to deck the coronal of 

 princes, or the marble statue to be reared to the 

 memory of worth or genius. Fossil shells were 

 elegantly termed by Bergman the " Medals of 

 Creation." The geologist reads in the masses of 

 species of shells now extinct, histories of by-gone 

 times and of earth's changes ; and distinctly 

 deciphers traces of revolutions, of which, but for 

 their aid, we should know nothing. Fossil shells 

 are among the most valuable records of the earth 

 on which we live. 



Though the study of the shells of land or sea is 

 important to science, vet Conchology is much less 

 popular than most 01 the other departments of 

 Natural History. It may be that it is owing to 

 the costliness of the pursuit. Foreign shells are 

 expensive, and even a good collection of native 



