462 M. FOSLIE. 



Among the calcareous algae in question which only, or almost only, occur on coral-reefs 

 and there play a prominent part as reef-builders, it seems as if the coarse Lithophyllum 

 craspedium may be placed in the front rank. Thus this species is apparently the predominant 

 alga in certain atolls of the Maldives (PI. XXV. fig. 1). The same species also abounds at 

 Funafuti, and at Onoatoa, Gilbert Islands, is a very abundant type. According to a label, 

 " this Nullipore, Finckh says, is actually the reef-former at Onoatoa. He saw no live coral 

 there, but everywhere on the lagoon and ocean-face immense masses of this particular 

 Nullipore." Next to the last named species, Goniolithon fi-utescens appears to be abundant in 

 the Maldives, and is there especially numerous on the sand-flat of Hulule, Male Atoll. This 

 rather finely branching species also occurs at Minikoi Atoll in the Laccadives. Further it is 

 common at Funafuti, where it was first met with, and the collector remarks that the species 

 is very abundant off the leeward (W.) islets, but is also found in great numbers in other 

 parts; he considers it to be a rather important reef-builder. A form of this species, repre- 

 sented by dead and fragmentary, apparently rather young specimens, also from Funafuti, has 

 been indicated as an important rock-former; the specimens comprise especially the crustlike 

 parts of the plants with short branches, but in contradistinction to other specimens are of 

 a hard consistency. They in part remind one of calcareous sediment, and are anastomosed 

 with fixed corals or fi-agments of corals. In addition, the crustlike Lithophyllum oncodes 

 appears to act as a kind of cement, and is apparently abundant in the Maldives as well as 

 at Funafuti and other places both in the Indian and Pacific Oceans. There are still a number 

 of other species, which in greater or less degree contribute to the formation of reefs, and 

 sometimes even form layers almost alternating with corals, Polyzoa, Foraminifera, etc. Their 

 occurrence and significance are, however, too little known to me to be specially mentioned here. 



It has been considered by some recent authors that algae having an incrustation of 

 carbonate of lime occur much more plentifully in the warmer than in the temperate oceans ; 

 or, in other words, a very slight amount of carbonate of lime is supposed to be developed 

 in the cold waters of the polar regions. According to our present knowledge of the distri- 

 bution of the Lithothamnia in different zones, this view is not correct. On the contrary, 

 numerous large banks of these algae are to be found in the Arctic as well as in the 

 temperate zone, though the number of species is less in the former seas. Thus on the coast 

 of Spitzbergen and Nowaya Zemlya Lithothamnion glaciale " covers the bottom in deep layers 

 for several miles, and altogether determines the general aspect of the vegetation, wherever 

 it occurs. In the formation of future strata of the earth's crust in this region it must 

 become of essential importance '." It is also known that Lithothamnion Ungeri forms banks 

 on the coast of Iceland, and also on the coast of Greenland. Indeed, these algae are 

 common and plentiful, partly even occurring in masses '. North of the polar circle on the 

 coast of Norway banks have been met with, which cover the bottom for several miles, and 

 plants appear in immense masses frequently representing only one species. Farther to the 

 south, for instance in the Trondhjem Fjord, rather large banks are to be found which may 

 be composed of a solitary small species such as Lithothamnion norvegicum, or other and 

 extensive banks of larger species which form deep layers built up in vertical direction, so 

 that they in part may be almost laid dry at lowest springs. In the same locality sub- 

 hemispherical specimens have been found, which vary up to half a metre in diameter, weighing 

 nearly 6 kilogrammes in a dried state. Similar specimens are also found on the south-west 



1 F. R. Kjellman, "The Algae of the Arctic Sea." * Kolderup Bosenvinge, Gronlands Havalger. Kjoben- 



Stockholm, 1883, p. 96. havn, 1893, p. 772. 



