— 206 — 



C. racemosa (Forsk.) W. v, B. var. Icetevirens, C. sertularioides (Gmel.) 

 and others. Of the fixed mud algae, Penicillus capitatus Lam. 

 appears in great numbers, and often grows so densely that it 

 covers the bottom altogether with its spherical heads, forming pure 

 Fenicilhis-Rssoc'miions. Here and there, but far less numerous, 

 species of Halimeda, e. g. H. incrassata Lamour. and H. Tuna 

 Lamour., are found growing in the same way. Halimeda Opuntia 

 Lamour. is often found lying on the bottom in large tufts and 

 between its entangled ramifications organic remains and mud gra- 

 dually accumulate to such an extent that the Halimeda sometimes 

 forms mound-like banks rising above the bottom; these are con- 

 stantly growing at the margin as the Halimeda grows new shoots 

 especially at the periphery. It may also be mentioned here that the 

 calcified algse, and especially perhaps the Halimeda-si^ecies, contri- 

 bute greatly, not only to the sand of the strand, which sometimes 

 consists almost entirely of fragments of Halimeda-io'mis, but also 

 to form deposits, both in lagoons as in the sea, in deeper but 

 sheltered localities where the bottom sometimes consists almost 

 entirely of Halimeda-gvsi\e\. This is the case for instance in the 

 Whites Bay near the south-west end of St. Croix, where at a depth 

 of 5 fathoms my dredge was over and over again filled to the 

 brim with Halimeda-jo'mis. 



The seagrass formation grows down to a depth of 5— 6 fathoms 

 probably deeper. On the west coast of St. Croix outside Frederiks- 

 sted I have thus seen it at this depth and I noticed here Thalassia 

 testiidinum Sol., Halodule Wrightii Aschers., Cymodocea manatorum 

 Aschers. and Halophila Baillonis Aschers., which by growing at 

 this depth were protected against the beating of the waves in this 

 open exposed locality. Of algae were found here as usual a number 

 of creeping Caulerpas and of attached Penicillus pyriforme Gepp 

 and several Halimeda-spedesi. 



The Algae formation on soft or sandy bottom extends to a far 

 greater depth, at least to 20 — 30 fathoms, consisting of Caulerpa- 

 species and of species belonging to the genera Penicillus, Udotea 

 and Halimeda. 



