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 Sondert 
and rather approaches certain forms of this species. On the other 
hand it somewhat approaches forms of L. californicum which 
Stick to an uneven substrat. 
Occurrence. Pacific coast of North America: Puget Sound, 
Whidbey Island, Wash., Setchell and Gardner, 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 fully 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 lie 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 

