HOWE 



PL 



Lithothamnium concretum, n. sp. 



FIG. 1. Photograph of radio-vertical section (from same specimen as fig. 2), showing cell struc- 

 ture, tetrasporic conceptacles, etc., enlarged 100 diameters. The surface of the thallus 

 is toward the right. 



FIG. 2. Photograph of radio-vertical section, showing zonations, tetrasporic conceptacles, etc., 

 enlarged 42 diameters. 



