10 ILLUSTRATIONS. 



Page. 



Figure 53. Obolella vermilionensis 598 



54. Acrotheie artemis ~. 634 



55. Acrotheie coUeni 641 



56. Acrotreta cariuata 680 



57. Acrotreta circularis 680 



58. Acrotreta kutorgai 692 



59. Acrothyra minor 717 



60. Nisusia rara 730 



61. Nisusia (Jamesella) lowi 734 



62. Nisusia (Jamesella) spencei 737 



63. Wimanella inyoensis 747 



64. Wimanella simplex 748 



65. Billingsella bivia 750 



66. Billingsella coloradoensis 751 



67. Billingsella marion 758 



68. Wynnia warthi 771 



69. Eoorthis newberryi 783 



70. Eoorthis thyone 789 



71. Eoorthis zeno 792 



72. Syntrophia cambria 800 



73. Syntrophia campbelli 801 



74. Syntrophia ? unxia 805 



75. Huenella lesleyi 807 



76. Huenella vermontana 809 



