256 KJELLMAN, THE ALG OF THE ARCTIC SEA. 
Remark. Gosr’s refusal to acknowledge as valid Arescnoue’s genus of Lithoderma 
is apparently occasioned by his having misunderstood ArgescHoua’s description of the 
so called unilocular sporangia (cp. Bot. Zeit. 1877, p. 532). Fig. 6 in tab. 26 shows 
these organs in the genus Lithoderma to differ most essentially in appearance, arrange- 
ment, and origin from the same organs in the species of the genus Ralfsia. The differ- 
ence is so essential that the alga in question cannot even, in accordance with the 
modern principles of the systematic arrangement of the Phwozoosporacee, be referred 
to the same family as the Ralfsie. It does not with regard to those organs agree with 
the Lnceliew, with which family Ralfsia must be placed, but rather with the Puncta-— 
riacee. It differs, however, so considerably from these in the morphological and ana- 
tomical character of the frond, that it cannot be referred to that family either. The 
genus Lithoderma is distinguished from all Phawozoosporacee proper that I know, by 
the so called multilocular sporangia (gametangia) being arranged in specific stands 
issuing from the surface-cells of the frond, and on this ground I have thought it best 
to make as yet a separate family; (tab. 26, fig. 7). The structure and development 
of the frond are also different in Lithoderma and Ralfsia. The former is in this respect 
analogous to Melobesia, the latter to Lithophyllum among the Corallinacee. 
Halitat. The present species is sublitoral, covering small stones on gravelly bottom 
in 5—15 fathoms water. It usually occurs gregarious, characterizing the vegetation of 
extensive areas. It is most often met with on exposed coasts. I have found it in the 
Polar Sea with zoosporangia multilocularia (gametangia) during the latter part of September 
and in December. 
Geogr. Distrib. It is probably circumpolar, though it is not known at present in 
the American Arctic Sea. I have found it most abundant in the eastern part of the 
Greenland Sea and in the Murman Sea. Its northernmost point is Treurenberg Bay 
on the north coast of Spitzbergen Lat. N. 79° 56’. 
Localities: The Norwegian Polar Sea: Finmarken, local and scarce at Maasé and 
Gjesver. 
The Greenland Sea: common and rather plentiful on the coasts of Spitzbergen. 
The Murman Sea: common and abundant on the west coast of Novaya Zemlya 
and Waygats. 
The White Sea: at Solowetzki Isles. 
The Kara Sea: pretty abundant at Uddebay. 
The Siberian Sea: Lat. N. 76° 8', Long. O. 90° 25’; Irkaypi, Pitlekay, and the 
Tshutsh-villages east of this point, at no place common or abundant. 
Baffin Bay: the west coast of Greenland, according to specimens collected by 
Prof. Tu. M. FRriss. 
Lithoderma lignicola nob. 
L. thallo crustas elongatas, plus minus confluentes formante; filis verticalibus ex articulis 20 vel pluribus, 
erassitudine longioribus vel wquilongis contextis. Tab. 26, fig. 8—11. 
