4 M. FOSLIE. [1900 



appears to be common, but forming only thin crusts on Corals 

 and other hard objects, it does not seem to any high degree to 

 contribute to the formation of new strata, although it sometimes 

 forms almost alternating layers with Corals, Foraminifera, etc. The 

 said form of the spedes is hitherto only known from a depth of 

 38—86 fathoms, but it probably also occurs higher up. 



In the last quoted considerable depth, calcareous Algæ have 

 not formerly been found alive. The depth in which these Algæ 

 live in southern seas is on the whole but little known. In the 

 northern hemisphere they are frequently to be found from the middle 

 part of the litoral region, here however only crustlike species, and 

 descend to a depth as a rule not exceeding 20 fathoms. They 

 are seldom met with in depths between 20 and 30 fathoms. Two 

 species which in northern waters descend farthest down, viz. Li- 

 thothamnion glaciale and Lithotliamnion læve, once have been 

 picked up alive from a depth of 44 fathoms, but the specimens 

 were not well developed. 



The other three species from Funafuti appear in the litoral 

 and uppermost part of the sublitoral region. Among these Litho- 

 phyllum craspedium attains a considerable size and occurs in cer- 

 tain localities in great numbers. According to the list of the collection 

 as well as to be judged from the collection itself, the species con- 

 tributes, together with divers animals, as an important reef former 

 at Funafuti. So also as regards Lithophyllum onkodes which in 

 the litoral region appears in nearly the same manner as Litho- 

 thamnion Philippi f. funafutiensis in deep water, partly forming 

 rather thick layers on rocks or Corals, partly almost alternating 

 layers with the latter. It affords, like Lithophyllum incrustans 

 in the northern hemisphere, an example of interesting struggle for 

 existence between calcareous Algæ and Corals, sometimes almost 

 amounting to symbiosis. The third species, Ooniolithon frutescens, 

 also appears to be abundant and contributes to the same building 

 work, althoug apparently not to the same degree as the other 

 two species. 



As remarked 1. c. the borings have been brought down to a 

 consideiable depth, and samples show that the calcareous Algæ 



