Part Ii. Structure and Habits of Trilobites 77

Internal organs and muscles 77 Alimentary canal 77 Ceraurus pleurexanthemus 79 Calymene senaria 80 Cryptolithus goldfussi 80 Summary 81 Gastric glands 82 Summary 84 Heart 85 Illænus 85 Ceraurus and Calymene 85 The median "ocellus" or "dorsal organ" 86 Nervous system 89 Various glands 89 Dermal glands 89 Renal excretory organs 90 Reproductive organs 90 Panderian organs 90 Musculature 91 Flexor muscles 92 Extensor muscles 92 Hypostomial muscles 94

Eyes 96 Summary 97

Sex 98

Eggs 98

Methods of life (See also under "Functions of the Appendages") 98 Habits of locomotion 99 Food and feeding methods 103 Tracks and trails 104