44 



above name, and perhaps also included in Areschoug's L.fasci- 

 culatum, which comprehends more species, but, as remarked under 

 L. crassum, I am most inclined to refer Lamarck's plant to the 

 latter. The named fragment is sterile, apparently branched in the 

 same manner as L. dimorphum, the branches being of the same 

 thickness as in the latter, with truncate tips. I found a solitary 

 sporangium in an overgrown conceptacle also agreeing with that 

 of the last named species, tetrasporic and about 90 jj. long and 

 40 /j- broad. 



Habitat. The plant lives on sandy and stony bottom, from 

 a little below extreme low-water mark to a depth of about 3 

 fathom, hitherto with certainty only found in a sheltered sound 

 with rather rapid tides. Specimens gathered in January were partly 

 sterile partly richly furnished with conceptacles of sporangia, most 

 of which emptied, and others with ripe sporangia. Among nume- 

 rous specimens collected in the former half of July a couple are 

 provided with the named organs in development. 



Occurrence. The only known locality is Frojen (Rottingsundet) 

 inSondreTrondhjem's Amt, local but abundant and forming banks. 



Lithothamnion dehiscens Fosl. mscr. 



L. fronde libera in fundo jacente, subglobosa, hemisphaerica 

 vel demum cava, fornicata, roseo-purpurea, irregulariter subdicho- 

 tome ramosa, ramis initio e centro solido, exiguo, undique egredi- 

 entibus, demum inferioribus erasis, uno alterove ramulo brevissimo 

 prseditis, prsecipue superioribus plus minus coalitis, teretibus, 2 mm. 

 crassis; conceptaculis sporangiferis convexiusculis, at parum pro- 

 minentibus, infra apices ramorum plerumque creberrimis, a superficie 

 visis diametro 300 — 350 /*; conceptaculis cystocarpiferis et anthe- 

 ridiferis conicis, acutis, his diametro 250 — 300 ft, illis 400 — 500 /*. 

 Sporangiis quaternas sporas foventibus, 120 — 180 /J. longis, 45—80 

 jj- latis. 



f. typica Fosl. mscr. 



f. ramis subaequalibus vel in parte thalli inferiore ssepe subat- 

 tenuatis, apicibus rotundatis vel obtusis, parte superiore fastigiatis.. 

 apicibus plerumque obtusis. Tab. 11 — 12. 



