Bull. U. S. F. C. 1890. Biology of the Oyster-Grounds of South Carolina. (To face page 362.) 
Plate LXVII. 
Fig. 1. A Photo-micrograph of the Diatom, Surirella gemma, enlarged 
about 1,600 Diameters. 
The tip of the frustule is alone given, to indicate the character and texture of the glassy surface. 
The photograph was taken with a one-fourth inch objective of Powell and Leland, by Prof. 
Wm. Stafford, of the College of the City of New York. 
Fig. 2. Food of South Carolina Oyster. A few of the typical 
Organisms (x 225). 
Numbers 1 to 20 are diatoms. 
1-5. Navicula (Bory). 
6. N. didyma (K). 
7. Pinnularia radiosa (?) (K. S.). 
8. Amphora sp. (K.). 
9. Pleurosigma fasciola (E. S.). 
10. P. littorale (S. >. 
11. P. strigosum (S). 
12. Actinoeyclus undulatus (K.). 
13. Coscitiodiscus radiatus (E. ). 
14. Cyclotella rotula (E.). 
15. Synedrasp. (E.). 
16. Diatoma sp. (De C.). 
17. Cymbellasp. (Ag.). 
18. Mastogloia smithii (Thw.). 
19. Triceratium alternans (Br. Bai.). 
20. Biddulphia sp. (Gr. ) 
21. Grain of pine pollen (Pinus rigida). 
22. Foraminifera (Rotalia). 
23. Zoospore (Ulva ?). 
24. Spicules. 
