The New Encyclopædia BritannicaEncyclopædia Britannica, 1983 - Encyclopedias and dictionaries |
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Page 340
... present , lack- ing fin rays ; persistent notochord , without bone or cartilage ; bony skeleton , when present , formed in skin ; true gill arches absent , gill basket present . Habitat of fossil groups uncertain ; earliest probably in ...
... present , lack- ing fin rays ; persistent notochord , without bone or cartilage ; bony skeleton , when present , formed in skin ; true gill arches absent , gill basket present . Habitat of fossil groups uncertain ; earliest probably in ...
Page 341
... present . One genus , Palaeospondylus , many specimens , probably of a single species . Length about 4 cm . CLASS SELACHII ( sharks , skates , rays , and relatives ) Vertebrates with jaws ; dermal and endochondral bone ab- sent ...
... present . One genus , Palaeospondylus , many specimens , probably of a single species . Length about 4 cm . CLASS SELACHII ( sharks , skates , rays , and relatives ) Vertebrates with jaws ; dermal and endochondral bone ab- sent ...
Page 343
... present are thin , overlap- ping plates of bone that continue to grow throughout life ; their lower jaws lack certain bones found in many chondros- teans or at least have some of these bones fused to single ele- ments ( see TELEOSTEI ) ...
... present are thin , overlap- ping plates of bone that continue to grow throughout life ; their lower jaws lack certain bones found in many chondros- teans or at least have some of these bones fused to single ele- ments ( see TELEOSTEI ) ...
Contents
would become the principal reserve asset while gold | 36 |
Excretion the elimination of the waste products of | 50 |
Volumes | 431 |
Copyright | |
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acid activity amount animals appears become blood body called carried cause cells century changes chemical close common complete consists containing continuous countries depends direction early effect evidence evolution example existence farm federal ferns fibres field Figure fire function gametophyte give groups important increase interest Italy kidney known later leaves less light lines living major marriage material means ment method move movements muscle natural normal obtained occur organs origin percent period person plants position possible present pressure problems produced properties protection reduced remain renal response result retina selection similar social species structure supply surface temperature tend tion types United urine usually various vary