352 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



Silurian era, Barrande's dis- 

 coveries in Bohemia, 322 



higher vertebrates un- 

 known, 321 



Siphonaria, 228 



Sirenians, as early terrestrial 



Ungulates, 208 

 Sivatherium, 212 

 Skeleton in Vertebrates, 87-9 

 Solenomya, persistent form of 



Lamellibranch, 163 

 Sozobranch stage of Haeckel, 5 5 

 Sozunan stage of Haeckel, 56 

 Spargidae, 220 

 Species and Genus in Zoology 



and Palaeontology, 184 



approaching decay of some 

 present species, 243 



Darwin on origin, 35 et seq. 



definition of, 185 



degeneration of, 217 et seq. 



dissociation of, 65 



extinction and its causes, 

 231 et seq. 



fixity of, abandonment of 

 hypothesis, 121 



great, do not pass gradually 

 from one to another, 147 



Lamarck on, 128 



method for delimitation of 

 142 



origin of (transfer mist 

 theory), 122, 265 et seq. 



passing from one stage to 

 another, d'Orbigny on, 20 



predestination hypothesis 

 as to duration, 235 



transition by sudden leaps, 

 70 



variability of, 63, 125 



variation in space, 125 etseq. 



variation in time, 149 et seq. 

 Sphcsrocerata, 214 

 Sphargis, 171 



Sphenodon, 171 

 Sphenoid bone, 87 

 Spirifers (Brachiopod), 159 

 Spiriferina, 239 

 Sponges, 46, 47 



Sponges, Silurian, 319 

 Spontaneous Generation, an- 

 cient and medieval ideas on, 



4, 24 



Lamarck on, 28 



Square bone (lower) of fishes, 88 



of Batrachians, Birds, and 

 Reptiles, 88 



Squatina (sea-angel), 170 

 Stegocephala, 198, 294 

 Stegodon, 179 

 Stegosaurus, 301 

 Steneofiber, 313 



Stephanoceras (Ammonite), 196 

 Stoliczkaice, 286 

 Stringocephalus (Brachiopod), 



165 



Stromatopores, the, 116 

 Struggle for existence, Darwin 



on, 36, 234, 265 



early views, 25 



Haeckel and Huxley on, 

 265 et seq. 



Struthiosaurus, 300 

 Suessia (Brachiopod), 239 

 Suidae (pigs, etc.), 112 



first appearance of, 311 

 Sumatra, white-backed tapir 



of, 8 



Symplectic bone of Fishes, 87 

 Synamceba, 46 



stage of Haeckel, 54 



TABLES, Ages of the Earth, 

 Plate I 



Animal Kingdom, Plate II 



Anthracotherides (Brachyo- 

 dus, etc.), 177 



Chasmotherium and Lophio- 

 don Branches, distribution in 

 Geological time, 201 



Evolution of Proboscidians, 

 1 80 



Phyletic Branches in geo- 

 logical time, 191 



Tabulate polyps, 93 

 Tachygenesis (Embryonic ac- 

 celeration), 254, 258 

 Tanystrophczus, 301 



