BY A. H. S. LUCAS. 179 



in our species, lint, as in Oscillatoria proper, forms occur both 

 with and without calyptrse, it seems better to include it with its 

 allies of similar habitat and habit. 



The specific name is derived from the Latin Scobs, saw-dust. 



EXPLANATION OF PLATE VI. 

 Laurencia infestans, sp.nov. 

 Fig. 1. — The plant. 



Fig.2. — A rhizoid expanding into an adhesive disc. 

 Fig.3. — Cross-section of ramus. 

 Fig. 4. — Ramulus with tetrasporangia. 

 Fig.."). — Cystocarps. 



