262 



FosLiE discusses (Remarks p. 113) the question, whether this species might 

 possibly 1)6 a northern form of Lithophyllum incnistans. This supposition would 

 not agree with the fact that the last named species, according to Mme Lemoine 

 (Struct, anat. pi. IV fig. 1), has a much developed hypolhallium. On the other hand, 

 a specimen collected by me at Cherbourg and determined by Foslie 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 Laesa, 4 — 5,5 meters, large crusts, Sept., no 5341 (see above). — 

 Ke: IR, Groves Flak, 24,5 meters: IK and IH, Lille Middelgrund ; lA, Store Middelgrund. — Ks: HO, 

 east of Hessela. Sii: 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 iwmen midum, 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), Foslie judged thai 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 hypolhallium formed by a single layer of inclined cells, in 

 contradiction to Eulithophyllum and Lepidomorphum, the hypolhallium 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 lo exist in the hypothallium being in Dermatolithon monostroma- 

 tical, while it is polystromatical in Lithophyllum ; but Foslie admits himself that 

 Ihe hypothallium may sometimes be partly polystromatical in Dermatolithon, (1909, 

 p. 57). And in Lithophyllum orbiculatum mentioned above there is evidently a mono- 

 stromatical hypolhallium (fig. 180). Further, in Dermatolithon, the cells of the hypo- 

 lhallium 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. 



