Bd. IV: 5) ANTARCTIC AND SUBANTARCTIC CORALLINACE.-E. 1 1 



f. compacta FoSL. 

 Alg. Not. 1. c. ; tab. nostr. 2, fig. 5. 



Syn. Lithophyllum capitulatum Heydr. Lithoth. Exp. antarct. ?>elge in Bull. Ac. R. 

 Belg. 1900, p. 560! 



The form which I have denominated f. circnniscripta is in fact only represented 

 by young or feebly developed specimens of the species such as it was first under 

 consideration, and such as it was first described. It is, therefore, questionable whether 

 it ought to be looked upon as an independent form. Indeed, it is more regularly 

 orbicular than young specimens of f. typica, and the conceptacles are partly a little 

 smaller. But still no proper line can be drawn, to judge from the material in hand. 

 The form corresponds to certain forms of Lithophyllum incrusians, as on the whole 

 L. discoid cum corresponds to and approaches the said northern species. 



The form 1 consider as the typical form of the species, is a rather coarse one, 

 but, when young, it shows the same state of things as the form last mentioned, 

 forming more or less orbicular crusts, which are, however, apt to be sooner con- 

 fluent than those of the said form. When, in growing, the crusts come in contact, 

 the edges colliding are frequently curved upwards and against each other, and gather 

 in dense, interlocking folds, the surface of which finall\- coalesces. The same is the 

 case even to a higher degree with some other species, e. g. Lithophvlhun incrustans 

 and Phymatolitlioii loculosiaii, sometimes also Ph. polymorphum. Besides, the crust 

 often develops irregular and rather coarse excrescences. This form recalls in habit 

 peculiarly intermediate forms of IJtJtopli. incrnstaiis f. Harveyi and f. angiilata. 



Of the form compacta only a single specimen is known. The form is closely 

 connected with f. iypica, but is distinguished b\- conceptacles more depressed, by 

 the greater thickness of the crust, which is up to 3 cm., and particularly by its 

 firmer consistency. It bears in habit a close resemblance to coarse and smooth forms 

 of Phymatolithon { Clathroii/orphitm) compactum and loculosiim. 



As I already mentioned in the first description, the species is rather varying as 

 to structure. Thus the perithallic cells, particularly in f. circumscripta, are often 

 shorter vertically than in other forms. Also in this respect L. discoideum shows 

 almost the same state of things as I., iucrnstans, the corresponding cells of f. de- 

 pressa of the species last mentioned being frequently much shorter than usual in 

 e. g. f. angidata. On the other hand small intermediate cells occur now and then 

 in L. discoideum as in Arcltœolithotliamnion. This is never the case with L. in- 

 crnstaiis. 



The conceptacles of sporangia in this species, when seen from the surface, are 

 first slightly conve.x, 180 — 250 u or up to 300 1.1 in diameter. Then they are fre 

 quentl}- decorticated and forming small point-like holes, as in Lithoph. incrustatis, 

 though shallower ones than in the latter. In a median vertical section they are 



