OF THE ‘PORCUPINE’ EXPEDITIONS. 475 
also brought up in dredgings made outside of this region in depths of 203 and 
290 fathoms, with temperatures of 47°-6 Fahr. and 41°5 Fahr. 
PLUMULARID. 
Among the eight genera to which the new hydroid species of the expeditions may be 
referred, no less than four belong to the family of the Plumularide—a family in 
which the dredgings were especialy rich, both in new species and in species which had 
been already described. Among the species now for the first time made known, are 
several highly interesting forms, which not only render necessary the construction of 
some new generic groups, but suggest the modification of some old ones. 
I propose to distribute the new Plumularide of the ‘ Porcupine’ expeditions under the 
following four genera—Aglaophenia, Halicornaria, Cladocarpus, and Diplopteron. 
AGLAOPHENIA. 
The genus Aglaophenia is here understood in a somewhat restricted sense, and must 
be regarded as limited by the following diagnosis :— 
Trophosome.—Hydrocaulus with pinnate ramification. Hydrothece usually with an 
intrathecal ridge. Nematophores fixed; lateral nematophores one on each side of the 
orifice of the hydrotheca; mesial nematophores adnate {05 a greater or less extent to 
the front of the hydrotheca. 
Gonosome.—Gonangia included in corbulz, each of which replaces an ordinary pinna. 
The presence of an intrathecal ridge, referred to in the above diagnosis, affords a . 
character hitherto overlooked in the descriptive zoology of the Plumularide. I have 
given this designation to a more or less obliquely transverse ridge, which occurs in the 
interior of the hydrothece of a large number of Plumularide, where it forms an imperfect 
septum, by which the hydrotheca becomes divided into a proximal and a distal portion. 
The form of this ridge varies, and will afford characters available in specific diagnosis. 
AGLAOPHENIA DROMAIUS. Plate LXVII. figs. 1, 1%, 1’, 1°. 
Trophosome.—Stem attaining a height of between five and six inches, simple, flexile, 
slender, not fascicled, divided into internodes of equal length ; pinne springing each from 
a point near the middle of an internode, alternate, rather distant, of nearly equal length, 
extending along the stem to within a short distance of its base. Hydrothece deeply 
concave in front just above the line of attachment of the mesial nematophore ; margin 
deeply toothed ; intrathecal ridge strong, commencing at the front of the hydrotheca just 
below the orifice by which the cavity of the mesial nematophore communicates with that 
of the hydrotheca, and thence extending backwards but not meeting the mesial line of the 
back; mesial nematophore adnate for about two thirds of its length to the front of the 
hydrotheca ; lateral nematophores of moderate size, slightly overtopping the hydrotheca. 
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