136 



15 — 20 six-angular muciferous canals. At maturity this portion 

 gets dissolved, afterwards the whole roof, then leaving a distinct 

 and deep circular hole of about the same diameter as in L. cir- 

 cumscriptum, or 200 — 300 /J-. If the conceptacles are densely 

 crowded also a part of the dissepiments get dissolved, though less 

 than in the named species, but I have not seen them being angular. 

 The sporangia are bisporic, about 150 — 200 fi long, 60 — 80 jx 

 broad and 20 — 25 \i thick. 



Relation to other species. This species is closely related to 

 L. circumscriptum, and it ought, perhaps, to be regarded a sou- 

 thern form of the latter. However, I have not seen any true 

 transition, and it differs in several particulars partly quoted above. 

 The surface is also in a younger stage more uneven than in older 

 crusts of that species, more irregular in outline, the peripherical 

 portion frequently thicker, adjacent crusts getting fully confluent, 

 the striae coarser, and also somewhat differing as to the structure. 

 So far as I have seen L. circumscriptum never produces excres- 

 cences. Besides, the conceptacles of sporangia are irregularly scat- 

 tered in every part of the crust, in certain states rather resembling 

 those of the named species, but on the other hand in the same 

 state of development somewhat differing, although I have seen 

 these organs only in some few specimens, most of which in 

 one and the same state, and I, therefore, do not know whether 

 they in this respect sometimes perhaps more approach the named 

 species. 



Habitat. Contrary to L. circumscriptum the present plant 

 apparently prefers sheltered places. I found it best developed in 

 a lagoon or streamlet with rather rapid tides, between half tide 

 level and high water mark in the innermost part of the Trondhjem 

 Fjord. Farther out the Fjord I met wtih it on a depth of 3 — 5 

 fathom, descending to about 10 fathom. Specimens collected in 

 the middle of August and October were furnished with ripe spo- 

 rangia, though very scantily, and some few of the conceptacles 

 were emptied. 



Occurrence. Hitherto only found in the Trondhjem Fjord, at 



