56 M. Foslie. 



Petrocelis, which I suppose belongs to this species. It grew 

 on a stone in the sublitoral zone, on a depth of about 3 fa- 

 thoms. 



Distribution: A single specimen found at Mehavn. 



Fam. Porphyracese (Kiitz.) Thur. 



in Le Jol. Liste Alg. Cherb. p. 16; Eiitz. Phyc. gener. p. 382; char, mut. 



Gen. Diploderma Kjellm. 

 N. Isb. Algfl. p. 236. 



Diploderma amplissimum Kjellm. 

 N. Ish. Algfl. p. 236. 



f. planiuscula nob. 



f. plana vel parce undulato-plicata; thalli parte media 40 — 60 [J. crasea, 

 eellulis in sectione transversa quadratis vel verticaliter subrectangularibus. 

 JBxsicc. Porphyra miniata Aresch. Alg. Scand. exsicc. Nr. 262. 



f. typica. 

 Descr. Diploderma amplissimum Kjellm. 1. c. 

 Fig. „ „ t. 17, fig. 1-3; 1. 18, fig. 1-8. 



f. tenuissima Stromf. (nob.) 

 Descr. Diploderma tenuissimum Stromf. Isl. Alveg. p. 33. 

 Fig. „ „ „ J- c. t. 1, fig. 17-18. 



Exsicc. Cfr. Porphyra miniata Collins in Hauck et Richt. Phyk. univ. No. 8. 

 Syn. Ulva umbilicalis ^ purpurea Wg. Fl. Lapp. p. 506. 



Porphyra laciniata f. linearis et vulgaris Kleen, Nordl. Alg. p. 23. 

 „ coccinea Kleen 1. c. p. 24. 

 „ miniata Aresch. Phyc. Scand. p. 407; ex parte. 



This species, as understood in the above taken sense, 

 includes several forms rather different, but on the other hand 

 nearly connected. Thus D, tenuissimum Stromf. in ray 

 opinion is but a form of D. amplissimum. At East-Finrnar- 

 ken I have collected specimens which fully coincide with 

 Icelandic ones in habit as well as structure, being 25 p. thick 

 with, in cross section, horizontally rectangular cells. But it 



