OP THE ' POECUPINB ' EXPEDITIONS. 477 



it better to employ the existing name of Halicornaria (though in a sense somewhat 

 diiFerent from' that assigned to it by Busk) for such Plumularidse as possess the tropho- 

 some oi Aglaoplienia but have their gonangia destitute of corbulee or other protection. 

 Among British species the genus would include the Plumularia jtennatida of Lamarck. 



Halicornaria eamulifera. Plate LXVII. figs. 3, 3% 3', 3% 3*. 



Troplwsome. — Stem attaining a height of about an inch and a half, slightly recurved, 

 simple, fascicled below, but becoming single towards the summit ; pinnae alternate, borne 

 each upon a short process of the stem and extending along the stem for about three 

 quarters of its entire height, longest towards the centre of the series, where they have 

 a length of about two lines, and thence decreasing in length upwards and downwards, 

 jointed, with each joint supporting a hydrotheca, and with its cavity constricted from 

 distance to distance by imperfect septa. Hydrotheca adnate to the pinna for a little 

 more than half its height, free for the remainder, adnate portion tumid, free portion 

 funnel-shaped, abruptly bent forwards, with its anterior wall forming nearly a right 

 angle with the adnate portion and having the margin deeply serrated ; no intrathecal 

 ridge ; mesial nematophore detached from the hydrotheca, and forming a stout free 

 tubular spine opening by a slit along that side which faces the hydrotheca; lateral 

 nematophores forming a pair of short tubular diverging spines ; a long jointed usually 

 simple ramulus, destitute of hydrothecse, given off from every joint of the pinnse 

 between the fundus of the hydrotheca and the mesial nematophore, emitting nemato- 

 phores from distance to distance and curving over the hydrotheca towards the distal 

 extremity of the pinna; main stem carrying a pair of nematophores at the base of 

 every pinna. 



Gonosome. — Gonangia (female V) ovate, with truncate summit, each springing from the 

 front c i one of the processes which are emitted by the main stem for the support of the 

 pinnae. 



This is a veiy distinct and well-marked form. It will be easily recognized by the 

 funnel-shaped and abruptly divergent distal portion of the hydrothecse, and by the long 

 ramuli, which do not develop hydranths and which are emitted by the pinnae at the base 

 of each hydrotheca. It is also rendered very remarkable by the way in which the 

 accessory ramulus interposes itself between the hydrotheca and its mesial nematophore. 

 It plainly constitutes a connecting link by which Aglaophenia passes into Plumularia. 



Halicornaria ramulifera was obtained in the deep cold area along with Thuiaria laxa, 

 Thuiaria kipimris, and Lafoea halecioides, from a depth of 640 fathoms, whei'e the 

 thermometer registered 30° Fahr., thus living in a temperature which was 2° Fahr. 

 below the freezing-point of fresh water. 



Cladocarpus, Allman. 

 Troplwsome. — Hydrocaulus with pinnate ramification. Hydrothecse with an intra- 

 voL. VIII. — PART VIII. April, 1874. 3 x 



