606 General and Applied Biology 



Actual preservation of the original material of the organism intact may 

 take place by freezing and preserving in ice or soil (Fig. 314). This is 

 not a common method, but an excellent example is the frozen mammoth 

 discovered in Siberia a few years ago. Even plants of the same period 

 were refrigerated with the mammoth. The complete remains of organ- 

 isms may be enclosed in rocks as illustrated by a leaf of a plant. The 

 remains of animals and plants may be preserved more or less intact in 

 tar, amber, or oil-impregnated soils (Fig. 316). Amber is a yellowish 



Fig. 313. — Fossils of invertebrate animals with the geologic period in which 

 each type was found (see Figs. 320-322). I, Protozoa, Foraminifera {Fusulina 

 secalica), Pennsylvanian epoch; II, Porifera, sponge {Astraeospongia meniscus), 

 Silurian Period; III, Porifera "Astylospongia" {Carpomanon stellatim-sulcatum) , 

 Silurian Period; IV, Coelenterata, horn coral {Zaphrentis prolifica) , Devonian 

 Period; V, Coelenterata, coral (Acervularia davidsoni) , Devonian Period; VI, 

 Coelenterata, honeycomb coral {Favor sites sp.), Devonian Period; VII, Echino- 

 dermata, sea bud or Blastoid {Pentremites sp.), Mississippian epoch; VIII, Echino- 

 dermata, stem or stalk of a Crinoid, Mississippian epoch; IX, Echinodermata 

 (Epiaster whitii) , Cretaceous Period; X, Brachiopoda, Brachiopod {Cyclothyris 

 difformis) , Cretaceous Period; XI, Brachiopoda, Brachiopod (Rafinesquina 

 alternata) , Ordovician Period; XII, Brachiopoda, Brachiopod (Spirifer pennatus) , 

 Devonian Period: XIII, Mollusca, Pelecypod {Glycimeris subovata) , Miocene 

 epoch; XIV, Mollusca, Gastropod (Bembexia sulcomarginata) , Devonian Period; 

 XV, Mollusca, Gastropod {Solutilites sayanus) , Eocene epoch; XVI, Arthropoda, 

 Trilobite {Calymene niagarense) , Silurian Period. 



