No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 125 



utriculosa from the Adriatic (f. intermedia). On Halopteris fllicina 

 from the same area I have seen it almost imbricate, or the edge 

 of the crust bends either upwards or downwards as in young 

 specimens of Lithothamnion lichenoides growing on smaller alga?. 

 This is sometimes the case also when the plant is growing on 

 Cystosira. In the Adriatic it sometimes also occurs on Peyssonnelia 

 Squamaria and P. rubra, partly even in layers twice or thrice 

 alternating with one of the said alga?. Here too it grows in part 

 freely and may then become concentrically zonate on the part 

 turning downwards. On the two host plants last mentioned it has 

 been found associated with Melobesia farinosa f. callithamnioides, 

 while on the others it often shares substratum with M. farinosa 

 f. typica. 



Already Rosa no ff 1. c. has enumerated several alga? on which 

 L. pustulatum is growing. Still several may be added. I will, 

 however, here only point out that it may also occur on chitin-tubes 

 of hydroids, perhaps also on mollusk shells. Thus I found, among 

 specimens of Cladophora prolifera and Corallina rubens from the 

 Adriatic, on which f. intermedia occurred in no small number, 

 some hydroids which were also covered with small crusts of the 

 same form. On the said hydroids it shared substratum with Me- 

 lobesia farinosa f. callithamnioides. Between the frond of Valonia 

 utriculosa from the same area, mentioned above, were attached 

 several quite small mollusks. On some of the shells were found 

 young and sterile crusts, probably belonging to L. pustulatum, 

 which was found numerously occurring on Valonia. At Round- 

 stone on the west coast of Ireland I fell in with f. Corallince 

 on specimens of Litliothamnion calcareum, which were growing 

 among Corallina officinalis, on which f. Corallince or a form pro- 

 perly identical with f. macrocarpa occurred in abundance. This 

 fact seems to me to impair the claim of the approaching L. hapa- 

 lidioides to be considered as an independent species. The form 

 growing on Litliothamnion fruticulosum mentioned in Lithoth. 

 Adriat. Meer. p. 28 perhaps belongs to L. pustulatum, although 

 also L. hapalidioides sometimes seems to occur on other calca- 

 reous alera?. 



