Ringed Worms (_see_ Annelida).
River-gravels, high-level and low-level.
_Robulina_.
Rocks, definition of; divisions of; igneous; aqueous;
mechanically-formed; chemically-formed; organically-formed;
arenaceous; argillaceous; calcareous; siliceous.
_Rodentia_, of the Eocene; of the Miocene; of the
Post-Pliocene.
Roebuck.
_Rostellaria_.
_Rotalia; Boueana_.
Rugose Corals; of the Lower Silurian; of the Upper Silurian;
of the Devonian; of the Carboniferous; of the Permian; of
the Upper Greensand.
Rupelian Clay.

_Sabal major_.
Sabre-toothed Tiger.
_Saccammina_.
_Saccosoma.
Salamanders.
Salina Group.
_Salix; Meeki_.
_Salmonidoe_.
_Sao hirsuta_.
_Sassafras cretacea_.
_Sauropterygia_.
_Scalaria; Groenlandica_.
_Scaphites; oequalis_.
_Schizodus_.
Schoharie Grit.
_Scolecoderma_.
_Scoliostoma_.
_Scolithus; Canadensis_.
Scorpions of the Coal-measures.
Scorpion-shells.
Screw-pines.
_Scutella; subrotunda_.
Sea-cows (_see_ Sirenia).
Sea-lilies (_see_ Crinoidea).
Sea-lizards (_see_ Enaliosaurians).
Seals.
Sea-mats and Sea-mosses (_see_ Polyzoa).
Sea-shrubs (_see_ Gorgonidae).
Sea-urchins (_see_ Echinoidea).
Sea-weeds.
Secondary period.
Sedimentary rocks.
_Semnopithecus_.
Septaria.
_Sequoia; Couttsioe; gigantea; Langsdorffii_.
_Serolis_.
Serpents (_see_ Ophidia).
_Serpulites_.
Sewalik Hills (_see_ Siwalik Hills).
Sheep.
Shell-sands.
_Sigillaria; Groeseri_.
Sigillarioids.
Silicates, infiltration of the shells of Foraminifera by.
Siliceous rocks.
Siliceous Sponges.
Silicification.
Silurian period (_see_ Lower Silurian and Upper Silurian).
_Simosaurus; Gaillardoti_.
_Siphonia; ficus_.
Siphonostomatous Univalves.
_Siphonotreta_.
_Sirenia_; of the Eocene; of the Miocene.
_Siren lacertina_.
_Sivatherium; giganteum_.
Siwalik Hills, Miocene strata of.
Skiddaw Slates.
Sloths.
_Smilax_.
_Smithia_.
Snakes (_see_ Ophidia).
Soft Tortoises.
_Solarium_.
Solenhofen Slates.
Solitaire.
_Spalacotherium_.
_Spatangus_.
_Sphoerospongia_.
_Sphagodus_.
_Sphenodon_.
_Sphenopteris_.
Spiders of the Coal-measures.
Spider-shells.
Spindle-shells.
_Spirifera; crispa; disjuncta; hysterica; mucronata; Niagarensis;
rostrata; sculptilis; trigonalis_.
_Spiriferidoe_.
_Spirophyton cauda-Galli_.
_Spirorbis; Arkonensis; Carbonarus; laxus; Lewisii; omphalodes;
spinulifera_.
_Spirulirostra_.
_Spondylus; spinosus_.
Sponges, of the Cambrian; of the Lower Silurian; of the Upper
Silurian; of the Devonia