EXPLANATION OF PLATES. 171 



Fio. J.— GRY H^A PrrCHERL 



Fig. 2 a. Exterior of upper valve. 

 2 b. Interior of the same. 



Fio. 3.— OSTREA SUBSPATDLATA. 



Fig. 3 a. Exterior view of the upper valve. 



3 b. Interior of the same. 



Fig. 4.— OSTREA BELLA. 



Fig. 4 a. View of the upper side of the two valves attached. 



4 b. Lower valve, exterior view. 



Fio. 5.— OSTREA LUGUBRIS. 



Fig. 5 a, b. Exterior and interior of lower valve. 



Fig. 6.— OSTREA CARINATA. 



PLATE XI. 



Fio. 1.— EXOGYRA MATHERONIANA. 

 Fig. 1 a, b. Exterior and interior views of lower valve. 



Fig. 2.— OSTREA VELLICATA. 



Fig. 2 a, b. Exterior and interior views of lower valve. 



Fig. 3.— OSTREA ROBUSTA. 



Fig. 3 a. Upper side, with the shell exfoliated. 



3 b. Lower side, retaining the shell, in part. 



Fig. 4.— OSTREA CORTEX. 

 Fig. 4 a, b. Exterior and interior of a lower valve. 



4 c, d. Exterior and interior of an upper valve. 



PLATE XII. 



FiQ. 1.— OSTREA MULTILIRATA. 

 Fig. 1 a, b. Exterior and interior of upper valve. 



1 c, d. Exterior and interior of lower valve, showing a dififerent form. 



PLATE XIII. 



Fig. L— NATICA TEXANA. 



Fig. 1 a, b. wo views of same specimen. 



Fig. 2.— NATICA COLLINA. 



Fig. 2 o, b. Two views of the same specimen. 



Fig. 3.— ROSTELLARIA ? COLLINA. 



Fig. 3 a, b. Two views of the same specimen. 



