HISTORY AND PROGRESS OF CONCHOLOGY. 3 



the higher orders ; also with certain glands for the secretion of a chalky, 

 inuculent matter, which is exuded during the growth of the animal, and 

 becoming hardened and moulded on the body, forms a firm calcareous 

 shell for protection or covering. 



The various colours and markings produced in the formation of the 

 shell are frequently of the most vivid and harmonious description, and 

 the varieties of form are elegant and symmetrical ; the outer surface is 

 often covered with a strong epidermis, and the inner parts, and those 

 enveloped by the mantle, are lined or coated with a clear polished ena- 

 mel ; the animal moreover has the property of restoring its shell in the 

 event of accident, until, from the commencement or nucleus of its birth, 

 it has performed the determined operation of growth. 



The system of reproduction in these animals is either oviparous or 

 viviparous ; they are marine, fluviatile, or terrestrial, distributed through- 

 out creation in greater or less abundance, but most prolific in the warm 

 and tropical regions, where, as in all other branches of Natural History, 

 the most beautiful forms and colours exist. 



The Indian and Pacific Oceans, the great rivers of America, the hills 

 and forests of Australia and the Philippine Islands, are all equally rich in 

 the production of these wonderful animals. In the sea they are found 

 in deep water, either living free, or attached to different marine sub- 

 stances ; sometimes buried in the sand, or fixed to rocks, timber, sea- 

 weed, &c. ; and they are also found boring, imbedded in coral, wood, or 

 stone. In rivers they float up and down with the tides, or adhere to 

 different vegetable substances ; and on the tops of hills and in forests they 

 are found on the branches of trees, creeping amongst the roots of shrubs, 

 or under the decayed and fallen leaves scattered on the earth. 



The system we adopt for our classification is distinctly based upon the 

 principles established by Lamarck, the alterations and additions which 

 the progress of science has rendered necessary so entirely according with 

 the general views of that great naturalist. It is true, that the arrangement 

 introduced by Gray contains many excellent genera, and is moreover 

 formed upon a skilful knowledge of the animal ; but we are of opinion 

 that the principle of subdivision is carried too far. The points upon 



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