Figures— Page 1. Sketch of a coprolite—fossilized animal excrement 14 2. Sketch of a gastrolith—the gizzard stone of an ancient reptile 14 3. Dendrites—a typical pseudofossil 14 4. Types of symmetry in a fossil coral 24 5. Bilateral symmetry in fossil brachiopod 24 6. A brachiopod showing specimen number and accompanying label 31 7. Two types of micropaleontological slides 32 8. Typical Pennsylvanian crinoidal limestone 41 9. Typical Texas Foraminifera 49 10. Typical radiolarians 49 11. Morphology and principal parts of corals 50 12. Two types of bryozoans 50 13. Morphology and principal parts of articulate brachiopods 54 14. _Lingula_, a typical inarticulate brachiopod 56 15. _Kingena wacoensis_, a common Cretaceous brachiopod 56 16. Morphology and principal parts of gastropod shells 60 17. Morphology and principal parts of a typical pelecypod shell 65 18. Morphology and principal parts of the pearly nautilus 75 19. Characteristic features of the various types of cephalopod sutures 75 20. Types of typical fossil annelid worms 78 21. Morphology and principal parts of trilobites 80 22. Two extinct attached echinoderms, _Pentremites_ and _Caryocrinites_ 81 23. Typical modern crinoid, or “sea lily,” showing principal parts 81 24. Graptolites 86 25. Sketches of mastodon and mammoth teeth 104 26. Two views of a typical fossil horse tooth 104