FosLıE discusses (Remarks p.113) the question, whether this species might 
possibly be a northern form of Lithophyllum incrustans. This supposition would 
not agree with the fact that the last named species, according to Mme LEMOINE 
(Struct. anat. pl. IV fig. 1), has a much developed hypothallium. On the other hand, 
a specimen collected by me at Cherbourg and determined by FosrıE as Lithophyl- 
lum incrustans, showed a one-layered basal layer and on the whole the same ana- 
tomical structure as L. orbiculatum. The question as to mutual relation of the two 
species must therefore be left undecided. 
The species has in the Danish waters only been found in the northern, eastern 
and southern Kattegat and in the Sound. It has been met with in depths from 
16,5 to 24,5 meters. The aberrant specimens were dredged in a depth of 4—5,5 m. 
Localities. Kn: TL, N.W. of Less, 4—5,5 meters, large crusts, Sept., no 5341 (see above). — 
Ke: IR, Groves Flak, 24,5 meters; IK and IH, Lille Middelgrund; IA, Store Middelgrund. — Ks: HO, 
east of Hessels. — Su: bM, south of Hveen, 12,5 meters. 
Subgenus Dermatolithon Foslie. 
As mentioned above, p. 236, the genus Dermatolithon was established by FosLie 
in 1898 (List of Spec., p. 11), only however as a nomen nudum, and the following 
species of Melobesia were referred to it: M. pustulata, Lejolisii and hapalidioides. 
In 1900 (Rev. syst. Surv., p. 21) the genus was described and M. macrocarpa was 
further referred to it, besides two uncertain species, while M. Lejolisii was removed 
from it. It was founded on characters of the sporangial conceptacles (comp. p 237). 
Later on (Algol. Not. I, 1904, p. 3), FosLıE judged that these characters were of small 
systematic value, he pointed out the relations of these species to the genus Litho- 
phyllum, and transferred Dermatolithon as a subgenus under Lithophyllum, charac- 
terized by having the hypothallium formed by a single layer of inclined cells, in 
contradiction to Eulithophyllum and Lepidomorphum, the hypothallium of which 
always consists of several cell-layers. Three years later (Algol. Not. VI, 1909, p. 58) 
FosLie raised it again to a distinct genus characterized only by the last-named 
character. As mentioned above, the species of Dermatolithon agree with Lithophyl- 
lum in the presence of transversal pits between the vertical cell-rows. A difference 
is certainly said to exist in the hypothallium being in Dermatolithon monostroma- 
tical, while it is polystromatical in Lithophyllum; but FosLie admits himself that 
the hypothallium may sometimes be partly polystromatical in Dermatolithon, (1909, 
p. 97). And in Lithophyllum orbiculatum mentioned above there is evidently a mono- 
stromatical hypothallium (fig. 180). Further, in Dermatolithon, the cells of the hypo- 
thallium are usually long and oblique, but they may also be rather short and 
only little inclined (fig. 189), which may likewise be met with in Lithophyllum, e. g. 
in L. orbiculatum, fig. 180 F. It must therefore be concluded that Dermatolithon 
cannot be kept distinct from Lithophyllum as a separate genus, at all events on 
the basis of the anatomical structure, but must be regarded only as a subgenus. 
