232. 
Frederikshavn; UC, TO, 18 m and FF (Trindelen) north of Læsø. — Ke: ZE, Fladen; IB, Store Middel- 
grund. — Km: XB and XC south of Kobbergrund. -- Ks: HS, Briseis Grund; OU, Schultzs Grund; 
00, Seborghoved Grund. — Sa: KK, Klergrund, south of Hjelm; FT, Klepperne. — Lb: Middelfart. — 
Sb: Reef at Korsor harbour, 2m; NN, south-west of Sproge, 19m. — Su: Off Aalsgaarde, 26m (H. E. 
Petersen); TF”, Staffans Flak, 14—18 m. — (Bm: Stones picked up near Stevns ?). 
8. Lithothamnion levigatum Foslie. 
Foslie, Norweg. Forms, 1895, p. 139, pl. 19, fig. 21—23; Heydrich, Lithoth. Helgoland, 1900, p. 76. 
Lithothamnion emboloides Heydrich, Lith. Helgol., p. 74, Taf. II Fig.-15 (teste Foslie). 
Phymatolithon levigatum (Fosl.) Foslie, Remarks. 1905, p. 79. 
Judging from Danish specimens, this species appears to be quite distinct from 
L. polymorphum, whereas, according to FosLıe (Remarks, p. 79), in more southern 
localities there is no distinct limit between these two species. L. levigatum is charac- 
terized by a comparatively thin, smooth crust, up to 0,5mm thick, by the roof of 
the sporangial conceptacles disappearing after the evacuation of the sporangia, and 
by the two-parted sporangia. When occurring together with L.. polymorphum, the 
difference between them is evident; the two species are, however, only rarely met 
with in the same locality, and it must be emphasized that L. polymorphum does 
not occur in the Limfjord, where L. levigatum has been met with in several loca- 
lities. I therefore do not doubt that they are specifically distinct. 
The anatomical structure much resembles that of L. polymorphum. The hypo- 
thallium is similar, but is sometimes more fully developed. Its cells were found to 
be 13—-21 y long, 4,5—7 » broad. The cells of the perithallium were less variable 
in breadth than those of L. poly- 
morphum; they were almost al- 
ways 6—7 y thick. The length 
. was usually 6—9y, most frequently 
7—8 vy, or only little greater than 
the breadth, and the rounded cells 
thus approach the spherical form; 
but cells shorter than broad are 
also met with (fig. 151 A). Trans- 
verse fusions occur here and there, 
in the hypothallium and the peri- 
thallium as well. Starch grains 
are frequently present as single 
grains in great numbers in most 
Fig. 150. 
Lithothamnion levigatum. Vertical sections of crust from Bolsaxen. 
Sb, showing sporangial conceptacles and limiting lines between the of the cells, except the uppermost. 
zones, fig. D also the hypothallium. 65:1. .. 
Only sporangial conceptacles were 
met with. They resemble those of L. polymorphum, and the hollow containing the 
roof is, as in that species, sometimes very slight or wanting, and the elevated border 
may also be wanting, the surface over the conceptacle thus being quite even or with 
