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Archaeolithothamnion,(Rothpl.) Fosl.*). 
1. A. Schmidtii Fos]. mscr. 
Thallus forming crusts on Corals up to about % mm. thick, 
sending forth crowded wart-like excrescences or short, simple or 
subsimple branches about 2 mm. thick, occasionally up to 12 mm. 
long, in an advanced stage frequently knotty and rugged and in 
part rather anastomosing. Sporangia 50—65 » long and 30—40 yu 
thick. 
There are to be found two specimens of this characteristic species, 
attached to about 15 cm. long and 3—5 cm. thick, somewhat compres- 
sed pieces of dead Corals which it at length fully surrounds. The crust 
does not attain any considerable thickness, apparently not exceeding about 
2 mm., frequently thinner. It produces in a rather young stage numerous 
small wartlike excrescences which little by little increase in size, becoming 
more and more crowded, frequently at length forming short, simple or 
subsimple’ branches 1.5—3 mm. thick, partly increasing in thickness up- 
wards partly not, or with somewhat spherical thickened ends, occasionally 
almost truncate, and in an advanced stage nearly always knotty and 
rugged. The branches are up to 12 mm. long, but generally smaller, 
in part at length rather anastomosing. New crusts sometimes are formed 
upon the primary, or now and then stretched between the branches, or 
irregular excrescences are formed by growing over extraneous objects. 
The surface is feebly shining. The colour was in a fresh state a brownish 
red, however almost discoloured in drying. 
On a vertical section the hypothallic layer is shown to be rather 
feebly developed, composed of elongated cells which are up to about 
20 long. It sends forth perithallic rows the cells of which frequently 
are 1*/2—2 times longer than broad, or 11—18 y long and 7—10p 
broad, here and there alternating with very small square or roundish 
cells. Between the more or less densely crowded overgrown sporangia 
(or cavities after these) the cells are as a rule much elongated and 
narrow. 
The sporangia are formed in more or less regular sori up to about 
3mm. in diameter. The sori are sometimes almost confluent, and ap- 
pear especially in the excrescences or branches, being dissolved or nearly 
so in the middle of February. On a section the overgrown sporangia 
form rather regular layers over each other and parallel to the surface of 
the frond. They are cylindric-bean-shaped or oblong, 50-—65 y long and 
30—40y thick, occasionally somewhat smaller and almost roundish- 
ovate. 
The species reminds one in habit of Lithothamnion rugosum Fosl. 
Otherwise it stands nearest to Archaeolithothamnion erythraewm (Rothpl.) 
Fosl., from which, however, it seperates itself by essential characteristics. 
Picked up from a depth of about 5 fathoms off Koh Kahdat, apparently 
scarce. 
1) With regard to the limit of the genera I refer to Revised Systematical 
Survey of the Melobesieae. Trondhjem 1900. 
