PLUMULARIA FILICULA. 29 
“= 
which is obliquely cut above and below so as to present two broad 
lateral teeth. 
Gonosome not known. 
In its opposite hydrothece adnate to the axis for only half their 
height, and disposed in distant pairs, this hydroid has so much of the 
aspect of a Sertularia that it might at first sight be easily referred 
to that genus. The fact, however, that the pairs of hydrothece are not 
separated from one another by a joint removes it from Sertularia, and 
notwithstanding the freedom of the hydrothece for so considerable a 
portion of their height, brings it into the genus Thuiaria.* 
It is a slender form, with a somewhat rigid habit which it would seem 
to owe to the non-jointed condition of the axis. 
Famiry PLUMULARIDA. 
Genus PLUMULARIA, Lamarck (in part). 
Plumularia filicula. 
Pie XV TLE thas. 1, 2. 
Trophosome. —Hydrocaulus attaining a height of about two inches, simple 
or with an occasional branch close to the root, not fascicled; pinne alter- 
nate, one borne by each internode of the stem, immediately below a joint, 
where it is supported on a long process of the internode; proximal inter- 
node of the pinne short and destitute of hydrotheca; following internodes 
elongate, every alternate one carrying a hydrotheca, the hydrotheca-bearing 
internodes slightly longer than the intervening ones. Hydrothecx small, 
each borne near the middle of its supporting internode. Supracalycine 
nematophores large ; a single mesial nematophore borne by the hydrothecal 
internode at the proximal side of the hydrotheca, two by each of the inter- 
vening internodes, and a single one by the short proximal internode. 
Gonosome. —Gonangia elongate, oval, smooth, narrowed below into a 
* I regard the presence of a joint at regular intervals between every two or every two pairs of hydro- 
thecz as an essential character of the true Sertularidans (Sertularia, Sertularella, Diphasia) quite irrespec- 
tively of the extent to which the hydrothece are adnate to the hydrocaulus. In Thuiaria, on the other 
hand, the joints occur at distant, and for the most part irregular intervals, thus allowing numerous hy- 
drothece to follow one another without any intervening joint. See Journ. Linn. Soc. Zodlogy, Vol. XII. 
p- 267. 
