MOSS CORALS. 91 



but they are found in every sea ; many of them 

 being used as food in tropical countries, on whose 

 coasts they are more numerous than in colder 

 climates. Some appear suspended from the vaults 

 of submarine reefs, others covering the more ex- 

 posed sides of rocks with a sort of flower, like 

 tapestry, and others confining themselves to the 

 smooth sands. 



Nearly allied to the genus actinia is that termed 

 Zoanthus ; the polyps, indeed, closely resemble the 

 actinia, but they are united together on a common 

 base, and are therefore, individually, not so inde- 

 pendent. 



There is a large class of animals, almost all of 

 microscopic minuteness, often called Bryozoa, or 

 moss corals. Of these, hundreds of microscopic 

 fossil species have been recently detected by the 

 researches and unwearied labours of Ehrenberg and 

 d'Orbigny ; and it would appear that their shelly 

 cases, or cells, enter into the composition of chalk 

 beds, compact mountain limestone, the flints of the 

 Jura limestone, the seasand of Europe, the Mau- 

 ritius, the Sandwich and adjacent islands, and the 

 sands of the Lybian desert. Many are invisible to 

 the naked eye; others resemble minute grains. 

 Of these fossil forms of bryozoa, not a few are 

 found still existing in a living state. Ehrenberg 

 has determined fifty- seven species in the Adriatic 

 sea and open ocean to be identical with fossil 

 species. 



