36 
pyrenoid (Fig. 4 g); in older filaments especially quantities of amylum 
are to be found. 
This species is found at St. Thomas: in the sea to the west 
of Water Island at a depth of about 20 meter; St. Jan: off Chri- 
stiansfort in about 30 meter of water, and near the isle Gt. St. 
James in the sound between St. Thomas and St. Jan at the same 
depth. 
By its more or less moniliform filaments this species may 
remind one somewhat of Avr. nigricans, but firstly the filaments 
in my species are not at all so regularly monoliform as in Avr. 
nigricans and further the filaments are much thinner. 
Compared with Avr. levis Howe of which I possess an original 
specimen kindly sent to me by Dr. Howe my species differs, be- 
sides its largeness, by having the filaments of the surface much 
more torulose than in Avr. levis where the outermost filaments run 
out in long, thin, only very feebly torulose threads. 
Avrainvillea spec. 
The colour of the single plant found when living I cannot tell, 
on drying it is grey-green with transition to a sordid-yellow; it 
has a short vertical rhizome covered with sand and gravel quite 
like those of e. g. Penicillus and Halimeda; then a slender stipe 
most probably somewhat flattened, on the dried specimen quite flat, 
especially in the upper part where it evenly passes over into the 
flabellum; the length of the stipe is 4!/2 cm., the breadth only 
about 4 mm.; the fiabellum is transverse-oblong, 8 cm. broad, 5/2 
high, thin, of a rather loose consistency with a more or less lacer- 
ated or lobed margin; the surface is somewhat uneven. 
Filaments in the interior of the flabellum (Fig. 6 a, b, c) cylin- 
dric or only very little torulose, about 30 4 in average diameter, 
only just below the dichotomy reaching 40 4 or even more, rather 
strongly constricted above the dichotomy and above the constriction 
in the thicker filaments often a single monoliform swelling; near the 
surface the filaments grow thinner (Fig. 6 d, €) becoming irregularly 
