303 
Both the form of the hydrothecae and their unilateral arrange- 
ment give to this species a great outer resemblance to Hydrall- 
mania falcata. 
Sertularia Nuttingi n.s 
(Pl. IV, figs. 1—4). 
The colonies, the largest of which has a height of 117 mm, 
have a thin slender: stem, whieh is as a rule only indistinetly 
divided into internodes, but in some. of them. the internodes of 
the distal part are rather distinct and each provided with 3 
branches. In the youngest colony, which has a height of 50 mm. 
and is provided with 15 pairs of alternate branches, the stem has 
very distinct internodes which are provided with 4—8 branches. 
We can discern in the colony between a proximal, somewhat 
longer part, in which the branches are simple and alternåte, and 
a distal part, the branches of which are composite and spirally 
arranged, the sixth being placed over the first. The latter branehes 
are provided on each side with 1—3 alternate branchlets, a few 
of which may rarely be bifurcate. The branches diminish in 
length towards the end of the branch, and as they have their 
ends lying in the same circle-segment these branches look as if 
they were flabellate. The simple branches and the longest branch- 
lets are only divided into two, rarely three internodes. 
The hydrothecae, which are alternate, show some difference 
in the proximal and in the distal portion of the colony, being in 
the former wholly adnate and provided with an almost vertical 
or very little ascending abcauline wall, while in the latter they 
have a very short, free distal end and a distinctly ascending ab- 
cauline wall. While further the single hydrothecae in the former 
are nearly approximate, they are in the latter divided from each 
other by an interstice Which may attain the half length of the 
hydrotheca. "The above differences, however, are not equally large 
in all colonies, and, besides, there may be found some difference 
also between the hydrothecae in the proximal and those in the 
