140 SEAWEEDS 



free or almost free from incrustation, while in others 

 each filament is thickly incrusted. In the latter case 

 they are constricted at short intervals like a string 

 of beads. Penicillus mediterraneus has a growth- 

 form formerly known as Espcra mediterranca, in 

 which there is no stalk, but all the filaments are 

 free. Similarly the species of Avrainvillea with free 



Fia. 38. Penicillus capitatus natural size. 



filaments and no stalk (A. comosa) were formerly 

 placed in a separate genus Chlorodesmis. A fossil 

 genus Ovulites from the Eocene (Paris basin) has 

 been placed here by Munier Chalmas, but though 

 there is no doubt it is a calcified siphoneous Alga 

 and does riot belong to the Foraminifera as formerly 

 thought, its position near Penicillus is not so certain. 



