Plate XIII. 



ORGANISMS CONSTITUTING FOOD OF MATAGORDA BAY OYSTERS. 



1-6. Navicula elliptica, x 660. (After 7. Pleurosigma intermedium, x 400. (After 



Schmidt). Smith.) 



8. Pleurosigma fasciola, x 400. (After 9-11. Navicula didyma, x 660 (After Schmidt. ) 

 Smith. ) 



