4 M. FOSLIE. [1902 



As remarked above the present species resembles Phymato- 

 lithon polymorphum in habit except with regard to the mentioned 

 reproductive organs. It stands nearest to Lithothamnion Sonderi 

 and rather approaches certain forms of this species. On the other 

 hand it somevvhat approaches forms of L. californicum which 

 stick to an uneven substrat. 



Occurrence. Pacific coast of North America: Puget Sound, 

 Whidbey Island, Wash., Setchell and Gard ner, No. 653. 



Lithothamnion Sonderi Hauck. 

 Meeresalg. p. 273. 



f. pacifica Fosl. mscr. 



Excrescences more dicidedly branchlike, cells sometimes larger 

 and conceptacles of sporangia less prominent than in the typical form. 



Along the Pacific coast of North America an alga has been 

 found, which at first sight seems to be ful ly identic with the 

 European L. Sonderi. A closer comparison shows however, that 

 in the American form the crust frequently develops excrescences 

 which are more decidedly branchlike than in the other, although 

 there appear specimens in both tracts which in this respect fully 

 resemble each other. Besides the said form differs a little in structure, 

 the cells on a cross section of the crust here and there being 

 slightly larger than in the typical form of the species. The con- 

 ceptacles of sporangia He a little deeper and therefore often being 

 less prominent than in European specimens, with most often thicker 

 roof. Therefore I consider this form a separate one and propose 

 to name it f. pacifica, It may however be remarked, that cysto- 

 carps are not yet known in the latter. In the typical form these 

 organs appear in other specimens than the sporangia, but it is 

 unknown whether so also being the case in f. pacifica, or whether 

 the conceptacles are of the same shape. 



The present form on the one side rather approaches L. rugo- 

 sum f. crassiuscula in habit. 1 have seen but a fragmentary spe- 

 cimen of the latter form which perhaps represents a separate species, 

 however at any rate more nearly connected with L. rugosum than 

 L. Sonderi. The form in question on the other hand sometimes 



