87 



f. papillata Fosl. mscr. 



f. crusta tenuiore, sublsevi vel tuberculis minutis instructa. 

 Tab. 17, fig. 22—23. 



Syn. Millepora polymorpha Mohr, Isl. Naturh. p. 141; ex parte. 



Spongites Crustacea Kiitz. Spec. Alg. p. 689; Tab. Phyc. 19, t. 97? 

 Lithothamnion purpureum Cr. Fl. Finist. p. 150; sec. spec. 



„ polymorphum Kleen, Nordl. Alg. p. 11; ex parte. 



„ „ Aresch. Obs. Phyc. 3, p. 5; ex parte. 



„ „ Hauck, Meeresalg. p. 271; ex parte. 



„ „ Kjellm. N. Ish. Algfl. p. 134(102); ex parte. 



„ „ Batt. Mar. Alg. Berw. p. 139; sec. spec; 



excl. syn. 



Remark on the limits of the species. Some forms formerly 

 referred to this species were removed by Kjellm an 1. c. It was 

 taken in the same sense by me in Contrib. I, most of the speci- 

 mens there referred to kindly determined by Kjellman and partly 

 recorded by him 1. c. However, regarding the plant distributed 

 by Areschoug in Alg. Scand. exsicc. No. 302 as the type, I am 

 now of opinion, that the species must still be limited and a form 

 removed from it, which in fact appears to be rather more nearly 

 related to L. glaciate. This I consider an independent species, 

 the before mentioned L. varians. I here record the present species 

 as defined by Stromfelt 1. c. in regard to the vegetative parts, 

 his specimens, as he remarks, also compared with Areschoug's 

 type specimen, and the below quoted shape and development of 

 the organs of propagation. 



Remark on the form of the species. This species seems to 

 be less varying than several other Lithothamnia, although there is 

 a rather considerable difference between the most extreme forms. 

 It perhaps includes more than the above quoted ones. They are, 

 however, not well defined, as transitions often appear to occur. 

 I do not know which of them might be considered the typical 

 form, nor have I seen any great number of specimens, as the plant 

 has been rather scarce in the tracts where I have collected Litho- 

 thamnia myself. 



The form tuberculata is characterized by its rather thin crust, 

 about 1 —3 mm. in thickness, which bears more or less numerous 



