123 



referred to rather different species, mostly, however, to L. poly- 

 morphum (L.). Crouan refers it to L. coralloides and Lamarck 

 to his Millepora informis, the latter referred by Crouan to his 

 L. polymorphum. The figure that Ellis gives of this plant some- 

 what reminds one of certain forms of the present species, but it 

 looks coarser and more clumsy- It on the other hand rather 

 approaches in habit a Lithothamnion that I got from Mr. Bat- 

 ters, gathered at Cum brae, which will be described in a se- 

 parate paper under the name of L. Battersii, but the latter is a 

 much smaller plant, the longest diameter only 1.3—2 cm., if, 

 however, Ellis' figure has not been magnified. 



The figure that Mohr 1. c. gives of one of the forms of his 

 Millepora polymorpha from Iceland is evidently f. squarrosa of 

 the present species. 



It seems as if Mill, polymorpha var. globosa Esper might 

 be referrible to this species. Fig. 1 1. c. reminds one much of 

 L. tophiforme f. globosa, and fig. 2 represents the upper part of 

 a branch-system apparently with conceptacles of sporangia and 

 cystocarps, supposed by Esper to be „die ersten Anlagen, oder 

 Schichten neuer Aeste", and also in this respect the plant rather 

 resembles L. tophiforme. However, it looks coarser and larger 

 than the last named f. globosa frequently appears to be, and is 

 fastened to another object. Lamarck, Philippi andAreschoug 

 refer -this plant to L. byssoicles, but the figure and description 

 make it little explicable that it can be any form of that species. 



One of the specimens figured by Johnston 1. c. (fig. 4) as 

 Nullipora calcarea most probably belongs to the species in ques- 

 tion, and appears to be nearly related to or identic with f. squar- 

 rosa. The other is mentioned under L. coralloides. 



It cannot with certainty be made out what Melobesia calcarea 

 Harv. really is. The figures in Phyc. Brit. 1. c. on the one side 

 much resemble certain forms of the present species, but on the 

 other side fig. 1 differs by its coarse main-axes. However, as 

 mentioned under L. flavescens the present plant is often infested 

 in the lower parts with other Lithothamnia, and then it sometimes 

 looks very coarse, especially if the branches also are somewhat 



