TABLE OF CONTENTS. 



Historical review 17 



Part I. The appendages of trilobites 20 



Terminology 20 



The appendages of Ncolemts 21 



Historical 21 



Neolenus scrratus (Rominger) 21 



Cephalon ; 21 



Thorax 22 



Pygidium 23 



Epipodites and exites 23 



Description of individual specimens 23 



Restoration of Neolenus 30 



Nathorstia transitans Walcott 31 



The appendages of Isotelus 32 



Historical 32 



Isotelus latus Raymond 34 



Isotelus maximus Locke 35 



Restoration of Isotelus 37 



Isotelus gigas Dekay 37 



Isotelus arenicola Raymond 39 



The appendages of Triarthrus (see also Part IV) 39 



Triarthrus becki Green 39 



Historical 40 



Restoration of Triarthrus 42 



Relation of cephalic appendagess to marking on dorsal surface of glabella 43 



Anal plate 44 



The appendages of Ptychoparia 45 



Ptychoparia striata (Emmrich) 45 



Ptychoparia cordillcra (Rominger) 45 



Ptychoparia permulta Walcott 45 



The appendages of Kootenia 46 



Kootenia dawsoni Walcott 46 



The appendages of Calymene and Ceraurus 46 



Historical . . 46 



Comparison of the appendages of Calymene and Ceraurus with those of 



Triarthrus 47 



Spiral branchiae 48 



Ventral membrane 50 



Appendifers . 51 



Calymene senaria Conrad 52 



Cephalic appendages 52 



Thoracic appendages 53 



Pygidial appendages 54 



