908] Collins,— Genus Pilinia 123 
The genus Acroblaste was founded on material from Buzzards’ 
Bay,! but no specific name was given; it was left in the unsatisfactory 
form Acroblaste spec., but with sufficient description and good figures. 
Wille? gave it the name Acroblaste Reinschii. There appears to have 
been no farther report of its occurrence in southern New England, 
but when a somewhat similar form was found at Revere Deach, 
Massachusetts, it was identified by the writer with Reinsch's plant, 
and was distributed under Wille's name as P.B.-A., No. 162. This 
plant, which was found only on the shells of Lunatia heros Adams, 
differed somewhat from Reinsch's description, but in the absence of 
any specimens, it was impossible to determine how much variation 
should be allowed for. Within the last two years the writer has 
found a plant at Mattapoisett, Wood's Hole and Eastham, all in 
southern Massachusetts, all agreeing with each other and with 
Reinsch's description and figures, without any tendency in the direc- 
tion of the differences shown by the Revere Beach plant. The latter 
has, moreover, been collected at all seasons of the year, and in no 
instance did it come any nearer to the southern form. Under these 
circumstances it seems best to consider it distinet, and to characterize 
it as follows:— 
P. Lunatiae n. sp. Acroblaste Reinschii Collins, List, RHODORA, 
Vol. II, p. 43, 1900, as to northern Massachusetts localities only; 
Collins, Holden & Setchell, P. B.-A., No. 162, 1896. Filamentis 
basalaribus mox in stratum subparenchymaticum concretis, cellulis 
forma ac magnitudine variantibus, rotundatis vel angularibus, ad 
15 « diam.; filamentis erectis 8-12 м diam., superne incrassatis, 
plerumque 5-6-cellularibus, rarissime usque ad 10-cellularibus, dense 
stipatis, ramificatione densa; cellulis ejusdem filamenti variantibus 
quoad formam et magnitudinem; sporagio e cellula terminali for- 
mato, a cellulis ceteris parum diverso; colore viridi intenso. 
Basal filaments soon becoming united into a subparenchymatous 
layer, cells of varying shape and size, roundish or angular, up to 15 & 
diam.; erect filaments 8-12 » diam., increasing in size upward, usually 
5-6 cells in length, quite rarely up to 10 cells, densely branched and 
very compact, cells varying in size and shape in the same filament; 
terminal cell becoming the sporangium, differing but little from any 
other cell of the filament; color deep green. On live shells of Lunatia 
heros Adams, Revere Beach, Massachusetts. 
1 Reinsch, Bot. Zeit., Vol. XXXVII, р. 361, Pl. III. A, 1878. 
2 Engler & Prantl, Nat. Pflanzenfam., Algen, p. 97, 1890. 
