12 THE APPENDAGES, ANATOMY, AND RELATIONS OF TRILOBITES. 



Relation of hypostoma to cephalon in Calymcne 55 



Restoration of Calymcne 56 



Calymcne sp. ind 56 



Ceraurus pleurexanthemus Green 57 



Cephalic appendages 58 



Thoracic appendages 59 



Pygidial appendages 59 



Relation of hypostoma to cephalon 59 



Restoration of Ceraurus pleurexanthemus 60 



The appendages of Aridaspis trentonensis Walcott 61 



The appendages of Cryptolithus (see also Part IV) 61 



Cryptolithus tcssellatus Green 61 



Restoration of Cryptolithus 62 



Summary on the ventral anatomy of trilobites 64 



Comparison of appendages of different genera 64 



Coxopodite 64 



Cephalon 64 



Thorax 66 



Pygidium ' 67 



Caudal rami 68 



Homology of cephalic appendages with those of other Crustacea 69 



Functions of the appendages 70 



Antennules 70 



Exopodites 70 



Endopodites 71 



Use of the pygidium in swimming 72 



Coxopodites 74 



Position of the appendages in life 74 



Part II. Structure and habits of trilobites 77 



Internal organs and muscles 77 



Alimentary canal 77 



Ceraurus pleurexanthemus 79 



Calymenc senaria 80 



Cryptolithus goldfussl 80 



Summary 81 



Gastric glands 82 



Summary 84 



Heart 85 



Illcenus 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 



