EXPLANATION OF PLATE XIL 



Fig. 1. Bkllkrophon chassits. (Page 157.) 



a. Dorso-lateral view. 

 Fig. 2. Euompiialds peknodosus. (Pago 156.) 



a. View of upper side. 



h. Umbilical view, sLowing the nodes. 

 Fig. 3. M.\crociieilu.s anguliferus. (Page 160.) 



a. A large example, having the angle unusually prominent and distinct. 



h. Auotber view of the same. 



c. A smaller example ; the angle less distinct. 



d. Another example, with angle distinct. 



e. Young example, iu which the angle is hardly perceptible. . 



/. Another example, in which the flattened upper side of the angle is very narrow. 

 Fig. 4. NATicorsis nana. (Page 159.) 



a. Example from Nevada. 



h. Another view of the same. 

 Fig. 5. Pj.atycer^\s Nebrascense. (Page 159.) 



a. An example from the typical locality in Nebraska. 



T}. Another view of the same. 



c. An example from near Santa F(S, N. Mex. 



cl. Auotber example, with angle distinct. 



e. Another view of the same. 

 Fig. G. Denialium canna. (Page 156.) 



a. A large example ; the outline showing the supposed full form. 



6. A mold of part of tbe surface, showing the minute longitudinal striaj. 

 Fig. 7. Ali.okisma snnoiiNEATA var. (Page 155.) 



a. Left valve. 



6. Front view. 

 Fig. 8. Aviculopecten occidentai.is. (Page 146.) 



a. Left valve. 



/). Eight valve. The specimen was imperfect. Tbe body of the shell should be at least one 

 third larger for ears of the size represented in the figure. 



