116 



viduals bearing conceptacles of cystocarps and, therefore, seldom 

 to be found on a section. 



Relation to other species. On the one side it closely approa- 

 ches certain forms of L. dehiscens and the limits are very difficult 

 to draw, although typically developed specimens of both are easily 

 .recognized. It scarcely can be considered only a form of that 

 species. On the other side younger or not opened and cup-shaped 

 specimens often are nearly impossible to distinguish from certain 

 forms of the following species, L. nodulosum, from which, howe- 

 ver, it is quite different in an older stage. 



Habitat. The species grows gregarious on rather hard bottom 

 in 5 — 10 fathoms water in protected places. Specimens collected 

 in the later half of July were sterile. 



Occurrence. Only known from Sorfjorden in the Skjorn Fjord 

 (a branch of the Trondhjem Fjord), local but abundant. 



Lithothamnion nodulosum Fosl. mscr. 



L. fronde libera in fundo jacente, subglobosa, diametro usque 

 -ad 10 cm., roseo-purpurea, decomposito-subdichotome ramosissima ; 

 ramis e centro solido, exiguo, undique egredientibus, subbrevibus, 

 inferne saspe plus minusve coalitis, teretibus, subcylindricis, circa 

 1.5 mm. crassis, extremis plerumque ramulos breves vel verrucae- 

 formes fasciculatos emittentibus; conceptaculis sporangiferis con- 

 vexiusculis, parum prominentibus, a superficie visis diametro 300 — 

 350 /J., conceptaculis cystocarpiferis depresso-conicis, apiculatis, dia- 

 metro 500 — 600 //.; sporangiis quaternas sporas foventibus, 130 — 

 180 ;x longis, 50—80 y. latis. Tab. 21, fig. 1—6. 



Description of the species. This plant always develops freely 

 on the bottom, forming subspherical masses, that attain a diameter 

 of up to 10 cm., frequently, however, less, or about 7 cm. PI. 

 21, fig. 1 — 6. The solid central mass is insignificant, and in older 

 specimens a smaller or larger part of the central portion is fre- 

 quently destroyed by boring-muscles or other animals. The frond 

 is repeatedly but rather irregularby subdichotomously branched. 

 The branches are frequently more or less curved, with short axes, 

 in the upper portions occasionally rather straight, terete and nearly 



