114 M. F0SL1E. [1905> 



specimens of Ph. compactum. Among the specimens examined 

 from the coast of Denmark, a specimen from Laeso also bears a 

 great resemblance in habit to Ph. compactum f. testacea, with 

 conceptacles smaller than usual in L. orbiculatum, and in this 

 respect standing in the same relation to specimens typically develo- 

 ped as f. testacea stands to a Ph. compactum typically developed. 

 Specimens from the south part of the Cattegat much resemble 

 young specimens of Ph. compactum f. coalescens. However, I 

 succeeded at length in finding characteristic conceptacles and 

 sporangia. Besides, the cells are usually smaller than in the species 

 last named. The alga in question sometimes also approaches in 

 habit Ph. Icevigatum and certain forms of Ph. polymorphum. 



Lithoph. orbiculatum occurs in the upper part of the sublitoral 

 region, attached to rocks or stones, in exposed localities occasionally 

 also in rock-pools in the litoral region, e. g. Faeo near Haugesund. 

 The best developed specimens I have seen I found at Tusteren in 

 a depth of 1 — 3 fathoms, rather abundant and partly growing in 

 company with a stunted form of Lithoth. Lenormandi. On the 

 coasts of Denmark, where solitary specimens are known from six 

 places, it has been collected in depths from 2 to 15 fathoms, partly 

 covering Phym. Imvigatum, partly and particularly sharing sub- 

 stratum with Lithoth. Granii. The species is sparingly furnished 

 with reproductive organs in the months of May and August — 

 September. 



As to the synonymy and the geographical distribution of this 

 species is to be remarked that I got a number of calcareous algas 

 some years ago from Port Renfrew (Port San Juan), Vancouver 

 Island, B. C, collected and kindly communicated to me by Mr.. 

 K. Yen do. Among these are a few specimens which coincide 

 in habit and structure partly with young specimens of Lithoph. 

 incrustans f. depressa, partly with L. orbiculatum. Therefore, I 

 mentioned in lit. this species as a form of L. incrustans. The 

 said form often grows together with another calcareous alga, or 

 one covering the other in various ways. However, as the said 

 specimens are sterile, and as I have lately seen how one species 

 often approaches another both in habit and in structure, I now do 



