EXPLANATION OF PLATE XIII. 



Fig. 1. Ni!;i;iTi.\A? PiiASEOLARis. (Pago 1G7.) 



a. View of upper side of example of uietlium size. 

 6. Lateral view of the same. 



c. View of the under side of the same. 



d. Small example, showing the suLall fold against the spire. 



c. Large example, showing the aforenamed fold, and also the obtuse revolving angle. 

 Fig. 2. Camptoxectes stygius. (Page 164.) 



a. Adult example, right valve. 



h. Small example, interior of right valve. 



c. Same, enlarged. 

 Fig. 3. OsTitEA STIJIGILICCLA. (Page 1G3.) 



a. E.xterior of the deeper valve, natural size, showing scar of attachment. 



ft. Lateral view of the same. 



c. Inside view of the same, showing parts about the hinge. 



f7. Interior view of the upper valve. 

 Fig. 4. Inocekamus crassalatus. (Page 16G.) 



a. Right valve, the largest in the collections. 



h. Another example, right valve.. 



c. Left valve, natural oast, showing the faint auricular furrow. 

 FrG. r>. Myophohia ambilineata. (P.age 1G6.) 



a. Eight valve, natural size. 



&. The same, enlarged. 

 Fig. G. Fextaci;inu.s ASTEULSCUS. (Page 1G2.) 



a. Articular face of a segment of the cohium. 



6. Portion of a column, showing the alternating larger and smaller segments. 



CRETACEOUS. 

 Fig. 7. Pinna I'ETiiiNA. (Page 182.) 



a. Right valve, natnral size. 



h. Transverse section of the shell a little behind the niidlcugth. 



