S saber-tooth cat: 102, 103 St. Mary’s University: 27 salamanders: 89 _Salenia_: 85 San Angelo College: 27 San Antonio College: 27 sand dollars: 82 _sapiens, Homo_: 22 Sarcodina: 47 Saurischia: 97 saurischians: 90, 97, 99 Sauropoda: 97 sauropods: 90, 97, 98 scale trees: 46, 47 scallops: 56, 59 Scaphopoda: 56 scaphopods: 26, 27, 28, 29, 56 _Schizodus_: 67 scientific names: 21-23 Scleractinia: 51 sclerites, holothurian: 83, 84 scolecodont: 78 scouring rushes: 47, 48 Scyphozoa: 49, 84 sea anemones: 49 sea cucumbers: 82 “sea lily”: 81, 82 “sea mats”: 51, 54 “sea-mice”: 56 sea urchins: 82 sedimentary rocks: 5, 19 _sellaeformis, Ostrea_: 72 septa, cephalopods: 66, 75 corals: 49, 51 serpent stars: 82 _Serpula_: 78 _Seymouria_: 92 sharks: 87 teeth: 10, 87, 88 sheep: 106 shrimp: 78 Siberia: 7, 106 _Sigillaria_: 46 _signata, Avonia_: 12, 13 silica: 10, 11 silicification: 11 Silurian— derivation and pronunciation: 34 fossils: 40 cystoid: 81 of El Paso and Van Horn regions: 40 skates: 87 slickensides: 16 slugs: 56 Smith, Fred: 1 snails: 11, 56, 59. _See also_ gastropods. snakes: 89 Solitario uplift: 40 Somervell County: 14, 15 South America: 87, 102 Southern Methodist University: 27 South Texas College: 27 Southwestern University: 27 species: 22 spicules, sponge: 49, 50 spiders: 78 spines, echinoid: 84, 85 _Spirifer rockymontanus_: 58 _Spirorbis_: 78 sponges: 10, 27, 30, 49, 50 spores: 47 _Squamularia_: 57 squid: 66, 78 starfish: 82, 83 _Stegosaurus_: 90, 97, 99 stegosaurs: 90, 97, 99 steinkern: 59, 62 stems, crinoid: 26, 28, 41, 81, 82, 83 Stephen F. Austin State College: 27 “stomach stones”: 14 stone, building: 19 Strabo: 3 _Straparolus_: 61 Strecker Museum: 95 _Striatopora_: 51, 52 _Strobeus_: 62 Styracosaurus: 90 _subhorrida, Avonia_: 12, 13 _subtilita, Composita_: 57 Sul Ross State College: 27 _Surcula_: 64 sutures, cephalopod: 66, 75, 78 nautiloid: 75 swine, giant: 106 _Sycostoma_: 64 symmetry: 23 bilateral: 24, 26, 29 radial: 24, 26, 28, 80