Two crustaceous brown algae from 
thè Danish West ladies 
by 
F. BOERGESEN 
At thè shores of thè Danish West Indies 1 have collected two 
crustaceous algae which I think worth mentioning. 
The one is a Ralfsia which I have referred to R. expansa ). 
Agardh, whose description of it is very incomplete, thè other 
Aglao^onia canariensis newly described by Professor Sauvageau. 
Ralfsia expansa J. A g. 
J. Agardh, Species Algarum, i, p. 63 ; Myrionema {}) expansum 
J. Ag., Nya alger fran Mexico (Oefversigt af K. Vetenskaps-Akademiens 
Foerhandlingar, 4, 1847, p. 5 , Stockholm 1848). 
Though using thè name of J. Agardh for this plant I may point 
out .that thè description of Agardh (1. c.) is so poor that an identi- 
cation by means of it is impossible and as, moreover, thè originai 
specimen of Ralfsia expansa, collected by Liebman at Vera Cruz 
and now in thè Botanical Museum, Copenhagen, is sterile, an exact 
identification by means of it is also excluded. In nevertheless using 
Agardh’s name it is mostly because thè sterile thallus of thè above- 
mentioned specimen of Liebman seems quite to agree with my spe- 
cimens and furthermore also, because thè plant in question has been 
found in nearly thè same flora-district. 
The plant when young forms orbicular later on more irregular 
crusts, often growing together to coriaceous expansions on stones 
and rocks. It has a dark brown colour. In young specimens thè 
surface is nearly even and smooth with more or less conspicuous 
