Plate III. 



III. Lagoons and mangrove swamps. 

 Fig. 



1. Littoridina, sp. Aperture, size -3-2 mm. 



2. Cerithidea mazatlanica Carpenter, 1856. Aperture, size - 26 ■ 11 mm. 



3. Cerithidea montagnei (Orbigny, 1837). Aperture, size - 30 > 17 mm. 



4. Anadara tuberculosa (Sowerby, 1833). A. Exterior, B. Interior, size - 65 x 45 mm. 



5. Crassostrca corteziensis Hertlein, 1951. A. Exterior, B. Interior, size - 80 x 45 mm. 



6. Crassostrea columbiensis Hanley, 1846. Interior, size -45 x 50 mm. 



7. Crassostrea corteziensis Hertlein, 1951. Interior, size - 126 x 60 mm (large example). 



8. Polymesoda olivacea (Carpenter, 1855). A. Exterior, B. Interior, size -21 x 18 mm. 



9. Polymesoda mexicana (Broderip and Sowerby, 1829). A. Exterior, B. Interior, 

 size - 42 :■: 43 mm. 



