EXPLANATION OF PLATE IX. 



Fig. 1. RllVNCIIONELLA EOCKYMONTANA. (PllgO 131.) 



a. Ventml valve, having only two plications in the sinns. 



b. Another ventral valve, having four plications in the sinus. 



c. Lateral view of another example, 

 rf. Kront view of the same. 



Fig. 2. Riiyncuonklla Uta. (Page 128.) 



fl. Ventral view of a largo example. 



b. Dorsal view of the same, p.artially restored. 



c. Lateral view of the same. 



Fig. 3. EnYxctiosELLA ? Wasatchensis. (Pago 130.) 



«. Ventral view of an example from the Wasatch range. 



6. Dorsal view of the same. 



c. Lateral view of the same. 



il. Front view of the same. 

 Fig. 4. Meekeli.a stisiatocostata. (Pago 126.) 



a. Ventral view of a globose form from Southern Iowa. 



b. Front view of the same. Convergence of stria3 near the margins of the valves imperfectly 



shown in the figure. 



c. Lateral view of the same. 



d. Ventral view of expanded variety. 



c. Posterior view of the same. 

 Fig. 5. Orthis Pecosii. (Page 125.) 



a. Ventral view of an example .a little above average size. 

 6. Dorsal view of tbe same. 



e. Lateral view of the same. 



d. Posterior view of the same. 



e. Dorsal view of a smaller example. 

 Fig. 6. CnoNETES platynota. (Page 121.) 



n. Ventral view of au averaged-sized example. 



b. Dorsal view of the same. 



e. Interior of a ventral valve, enlarged. 



d. Posterior view of areas, enlarged. 



0. Vertical section along the median line, enlarged. 

 Fig. 7. Chonetes mesoloua. (Page 123.) 



a. Ventral view, enlarged. 

 Fig. B. Ciioxetes graxulifera. (Page 122.) 



a. Ventral view; hinge-line less extended than usual. 



b. Ventral view of another example. 



c. Dorsal view of the same. 



