ITS FAUNA. 61 



existing seas and estuaries are in great part composed of the 

 shelly coverings of the minute foraminiferse, and the sili- 

 ceous muds composed of the still minuter shields of in- 

 fusoria, so we shall afterwards find that extensive strata in 

 the earth's crust owe their formation to similar agencies. 

 Next above these lowest forms of life stand the Kadiata 

 the corals, sea-anemones, jelly-fish, star-fishes, and urchins 

 all, too, inhabitants of the ocean, and in one or other of 

 their orders appearing in every depth and in every latitude 

 of space. Elaborating from microscopic organisms, the 

 material of their pulpy fabrics, which in turn become the 

 food of the higher orders, their function, though more 

 largely biological than the protozoans, is still in a great 

 measure formative. To coral-zoophytes we owe our exist- 

 ing coral reefs, and from the same source, or from their 

 allies the encrinites, have sprung many*of the massive lime- 

 stones that give character to the crust of the globe. The 

 office of the radiata is thus comparatively humble, as their 

 organisation, though beautifully symmetrical, is simple and 

 lowly. Next we approach the Molluscoida, or mollusc- 

 like organisms of modern naturalists the sea-mats and 

 dead-men's fingers of the fisherman and common observer. 

 Fixed in their habitats, and elaborating, like the corals 

 and sponges, their structures from the waters of the 

 ocean, their functions are humble and their characters 

 obscure. From them we ascend in the zoological scale 

 to the true Mollusca the oysters, mussels, cockles, whelks, 

 snails, slugs, nautili, and cuttle-fishes the " shell-fish" of 

 everyday language, though many of them are naked and 

 altogether shell-less. Of more diversified organisation than 

 any of the preceding groups, they are, in one or other of 

 their orders, inhabitants of the ocean, the lake, the river, 

 the marsh, and the dry land. Having also a more cosmo- 

 politan range feeding, some on plants and others on ani- 



