ila B< si. Reef. 

 Stal Lithothamnion bank in 18 — 36 ni. 



Sta; .-ii Nusa Besi and the N.E.-point of Timor. 27 — 54 m. Sand, coral and 



Lithothamni 



As mentii (1. c), I have not been able to draw any definite line between 



the type of tliis sp from the coast of Brazil and the nearly allied forms occurring in the 



Indic and I ans. The former I have named f. americana. Cp. fig. 15, representing 



the three specimens of this form hitherto 

 known, on which was based the original 

 description of the species. Fig. 1 5 B shows 

 one of the specimens seen from the side. 

 A reproduction of the same specimen is to 

 be found on pi. III, fig. 20, here seen from 

 above. Also from Bermuda a couple of 

 specimens are known, which seem to have 

 to be ascribed to the same form of the 

 species, though the cells are here partly a 

 little smaller than in the type specimens. 

 From the same spot I have classified a form 

 which I have named f. prostrata l ). 



Before entering upon the forms occur- 

 ring in the East-Indian Archipelago which 

 seem to have to be ascribed to the same 

 species, I want to make some remarks as 

 to the geographical distribution of this group 

 of algae. 



Viewed apart from some few species 



of the genus JMcloècsia, which are forming 



thin crusts on other algae and are widely 



distributed in the Atlantic as well as the 



Indian Ocean and parts of the Pacific, 



the geographical distribution of the other 



unarticulated calcareous algae of this tribe is still rather uncertain and unsufficiently explained. 



I have carlier pointed out the fact that they are often very local. As efficients of essential 



importance are also to be considered the facts that they partly, or rather usually, lay other 



claims to the physical quality of the bottom than the majority of other algae, and that their 



rrence is very dependent on sets of currents and tide. Owing to these circumstances the 



are often much varying, and occur here and there in forms more stunted than perhaps 



group of other Florideae, and in forms which may be almost unrecognizable and generally 



only occur as sterile or sparingly feftile. This is, however, also to a great extent due to the 



Fig. 15. Lithothamnion crubescens f. americana Fosl. 



The type specimens from Fernando do Noronha; 



B also represented pi. III, hg. 20. seen from above; nat. size. 



e. — Det Kgl. Norske Vidensk. Selsk. Skiïfter. 1900. n" 0. Trondhjem 1901, p. 3. 



