76 ZOOLOGY. 



These animals are microscopic, glutinous, and translucent, but tinted with 

 bluish, reddish, brown, or yellow, the tints being uniform in each species. 

 The soft parts are inclosed in a calcareous (rarely cartilaginous) shell, 

 fitted to the varied outline of the body, and presenting numerous variations 

 in form, affording characters for genera and higher groups. It has one or 

 more openings, or numerous pores, which allow egress to certain filaments 

 used as organs of locomotion. These can be extended to six times the 

 diameter of the body, and they recall the allied organs in the Echinodermata 

 and Cirrigrada. They are ramified like the branches of a tree, and have 

 the power of secreting calcareous matter upon the outside of the shell, in 

 which they resemble the extensions of the mantle in some orders. The 

 characteristic name Rhizopoda of authors, has been drawn from these 

 filaments. 



The Polythalamia inhabit most seas, and they are so abundant that 

 D'Orbigny calculated that an ounce of sand from the Antilles contained 

 8,840,000 individuals. The same author informs usthat these little beings 

 from a sixth to half a millimetre long, are more abundant than the minute 

 <'rustacea, or the infusoria whose shields form the tripoli of commerce. 

 Banks are formed by them dangerous to navigation ; they obstruct bays and 

 straits, of which the celebrated harbor of Alexandria is an example ; and 

 with the coralligenous zoophyta they form reefs and islands. 



In a fossil condition they are no less conspicuous. In Russia calcareous 

 beds are formed by a single species of Fusulina, and various species enter 

 largely into the composition of chalk and certain tertiary formations. They 

 are so abundant as in some cases to amount to 3,000,000,000 in a cubic 

 metre; and the city of Paris and the surrounding towns are almost built of 

 them, so abundant are they in the materials used. Dr. Buckland makes 

 the folloM'ing remarks: "'Xummulites are so called from their resemblance to 

 a piece of money ; they vary in size from that of a crown piece [!] to 

 microscopic littleness, and occupy an important place in the history of fossil 

 shells, on account of the prodigious extent to which they are accumulated 

 in the later members of the secondary, and in many of the tertiary strata. 

 They are often piled on each other nearly in as close contact as the grains 

 in a heap of corn. In this state they form a considerable portion of the 

 entire bulk of many extensive mountains, e.g. in the tertiary limestones of 

 Verona and Monte Bolca, and in secondary strata of the cretaceous forma- 

 tion in the Alps, Carpathians, and Pyrenees. Some of the pyramids and 

 the sphinx of Egypt are composed of limestone loaded with nummulites. 

 It is impossible to see such mountain masses of the remains of a single 

 family of shells thus added to the solid materials of the globe, without 

 i-ecoUecting that each individual shell once held an important place MÜthin 

 the body of a living animal ; and thus recalling our imagination to those 

 distant epochs when the waters of the ocean which then covered Europe were 

 filled with floating swarms of these extinct molluscs, thick as the countless 

 myriads of Beroe and Clio hm^eaUs that now crowd the M'aters of the 

 polar seas. Lamarck, in his observations on Miliola., remarks that these 

 very minute animals have had much more influence on the masses which 

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