233 
only a feeble trace of deepening or elevation (fig. 150 C). The roof is sometimes 
convex, though inserted in the bottom of a hollow. The sporangia are, as stated 
by FosLiE, always two-spored. I found them to be 95—126 „ long, (18—)37—53 4 
broad, thus a little smaller than the dimensions found by Foszie, which might 
perhaps partly be caused 
by the fact that my mea- 
surements have mostly 
been made with dehydra- 
ted sections. The concep- 
tacles are sometimes co- 
vered bya particular tissue 
similar to that mentioned 
for L. polymorphum (p.230). 
It has also been mentioned Zum: 
by HEyprIcH and FosLie 
(Remarks, p. 80). Accor- Cc 
ding to the first named Fig. 151. 
author (i. ce. p. 76) it is al- Lithothamnion levigatum. A, vertical section of hypothallium and the under 
o part of perithallium. B, vertical section of crust with emptied sporangial con- 
Ways present in L. em- ceptacle filled with regenerative tissue, showing the outlines of older filled 
boloides which, as shown conceptacles C, vertical section of empty conceptacle with covering tissue. 
x à F A 350:1. B-C 65:1. 
by FostıE, is identical 
with L. levigatum; it is, however, not suitable for use as a specific character, for in 
some specimens it covers all or nearly all the conceptacles, while in others it is 
almost or entirely wanting. I have only seen it on emptied conceptacles which 
still showed muciferous canals (fig. 151 C). It has a white colour. 
After the evacuation of the sporangia, the roof falls into decay. A regenera- 
ting tissue, produced from the bottom of the conceptacle, consisting of ascending 
filaments, may then fill the empty cavity. A new conceptacle is frequently produ- 
ced at so small distance over the first one that the base of the second is situated 
within the limit of the first, and the new one is thus partly produced by the re- 
generating tissue (fig. 150,151). Overgrown empty conceptacles do not occur. 
The species occurs in depths of 2—24,5 m, most frequently 5—20 m, growing 
on stones and on Mytilus and Ostrea, often in company with other Lithothamnia, 
as L. Lenormandi, L.glaciale and L. polymorphum. It has been found growing over 
L. glaciale, and in one case on the frond of Chondrus crispus. It has been found 
with ripe sporangia in April and May. 
Localities. Ns: aF, N.W. of Thyboren, 31 m. — Sk: 4 miles N.1/sE. of Svinklov beacon, 9 m 
(A. C. Johansen); SY off Løkken, 13m; ZK®, off Lønstrup, 12 m; off Hirshals (Børgesen). Lf: Salling- 
sund near Nykøbing (Th. Mortensen, !); LS!, 5,5 m and aT!, 4—5 m, east of Mors: Livø Bredning (C. H. 
Ostenfeld); Lendrup Ren. — Kn: Herthas Flak, 19—22 m; east of Deget near Frederikshavn; Trindelen, 
near the double broom (Børgesen). — Ke: IL, Fladen, 24,5 m; OO, Søborg Hoved Grund, 8,5 m. — Ks: 
RL, north of Gilleleje, 15m; HO, N.W. of Gilleleje, 22,5 m; OS, Hastens Grund, 14m. — Sa: KM, east 
of Oreflippen; BE, off Sletterhage; YV, east of Samso, 15 m; north side of Refsnæs, 19 m (C. H. Ostenfeld); 
D. K. D. Vidensk. Selsk, Skr,, 7. Række, naturvidensk. og mathem. Afd. VII, 2. 30 
