2.] • 5 



viduals on a depth of 5—15 fathom, fastened to smaller stones 

 or to Lithothamnia. Here it attains a diameter of up to about 20 

 cm., frequently, however, only the half or less, and most of the 

 specimens collected have been rather young. Exceptionally I met 

 with old individuals lying loose on the bottom, but these probably 

 have been loosened from the substratum by external causes. It 

 is very much varying as to the spape. The larger specimens are 

 irregularly lobed or sinuate, more rigid than those from the nor- 

 thern part of the coast, and rather crisp, with a broadly cordate 

 or sometimes even nearly saggitate and deeply cleft base, somewhat 

 undulate, often with extremely irregular margin, which here and 

 there is crenulate but more frequently dentate. The frond is so- 

 mewhat varying in thickness, up to about 250 //., but in general 

 about 150—200 />-, and here and there perforated. The structure 

 fully accords with that in specimens from the north, only the 

 cellulae glandulinae sometimes being less numerous. With refe- 

 rence to colour old specimens are much darker than younger 

 ones, and the former do not adhere to the paper, while te latter 

 sometimes adhere rather well sometimes not. 



Prof. Schmitz remarks 1. c. that there could be reason to 

 doubt whether T. septemtrionalis and T. Pennyi (Harv.) are spe- 

 cificalry distinct, or the former only to be considered as a young 

 stage of the latter- But on the other hand is to be opposed, as 

 he remarks. that in a small and typical specimen of the former 

 have been found well developed carpogons and that the true 

 T. Pennyi has not yet been found at Spitzbergen, Novaya Zem- 

 lya and Norvay, where T. septemtrioncdis occurs. He supposes, 

 therefore, that they are to be concidered as distinct species. How- 

 ever, the form of the species found ind the Trondhjem Fjord 

 shows, that the difference between these two species is even less 

 than supposed by Schmitz, or in fact they accord with one 

 another except therein, that the one (T. Pennyi) gets a little thicker 

 and always has been found lying loose on the bottom, but 

 the other, at least as a rule fastened to any harder object and 

 provided with a very short stipe, which, so far as I know, never 

 has been seen in T. Pennyi, or specimens found that appear to 



