TABLE OF CONTENTS. 13 



Panderian organs 90 



Musculature 91 



Flexor muscles 92 



Extensor muscles 92 



Hypostomial muscles 94 



Eyes 9 6 



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 



Part III. Relationship of the trilobites to other Arthropoda 106 



Crustacea : 106 



Branchiopoda 106 



Burgcssia bclla Walcott 108 



Waptia fieldcnsis Walcott 108 



Yohoia tenuis Walcott 109 



Opabina regalis Walcott 109 



Summary 109 



Copepoda no 



Archicopepoda in 



Ostracoda 112 



Cirripedia 113 



Malacostraca 113 



Phyllocarida 113 



Syncarida 114 



Isopoda 114 



Marrella splendens Walcott 115 



Restoration of Marrella 116 



Arachnida 1 17 



Trilobites not Arachnida 117 



Merostomata 119 



Sidneyia ine.vpectans Walcott 119 



Emeraldella brocki Walcott 119 



Malaria and Habelia 120 



Araneae 121 



Insecta 122 



Chilopoda 123 



Diplopoda 124 



Primitive characteristics of trilobites 125 



Trilobites the most primitive arthropods 125 



Limbs of trilobites primitive 125 



Summary 128 



Number of segments in the trunk 128 



