HALOPTERIS CARINATA. 333) 
The genus Halopteris constitutes an intermediate form between Aglao- 
phenia and Plumularia. To Aglaophenia it shows an affinity by its 
paired nematophores being adnate to the hydrotheex, and by its fixed 
monothalamic mesial nematophores with slit-llike aperture. To Plumularia 
it is connected by having more than one azygous nematophore seated 
on each internode of the pinne, and all at a distance from the hydro- 
theca, by the wide separation of the hydrothece from one another, and 
by their even margin. 
Halopteris carinata. 
Pi. XIX. Figs. 3-7. 
Trophosome. — Hydrocaulus attaining a height of about two inches, 
simple, non-fascicled ; pinnz alternate, springing one from each internode 
of the stem, near its proximal end; internodes of pinnx separated from 
one another by oblique joints, each carrying a hydrotheca near its mid- 
dle. Hydrothecz very large, adnate to internode for about two thirds of 
their height, and then becoming free, deep, nearly cylindrical in lateral 
aspect, infundibuliform in front aspect, margin even, with a_ slightly 
prominent cusp in front, from which a slight keel is continued for some 
distance along the front of the hydrotheea. Lateral nematophores in 
the form of a long tubular stalk which springs from the internode at 
a point near its middle, and thence passing obliquely across the side of 
the hydrotheca, reaches the margin, where it terminates in a cup-like 
dilatation. Mesial nematophores free, fixed by a narrow base, two on 
each internode, one being just below the hydrotheca, and one at a 
little distance above it. 
Gonosome not known. 
Off Carysfort Reef, from a depth of 35 fathoms. 
This is a remarkable hydroid, rendered striking by its long tubular lat- 
eral nematophores, and by the peculiar form and large size of its hy- 
drothece. The stem carries between the pinne longitudinal rows of 
short fixed nematophores whose oblique aperture is continued into a 
lateral slit. Though the mesial nematophores of the pinne are attached 
by a narrow base, they are firmly fixed, thus, along with the nemato- 
phores of the stem, contrasting with the movable and easily detached 
nematophores of the true Plumulariz. In this respect, and in their 
oblique and slit orifice, they resemble the nematophores of Aglaophenia. 
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