38 THE VOYAGE OF H.M.S. CHALLENGER. 
Aglaophenia attenuata is a small and delicate species.. The anterior bifid tooth of 
the hydrotheea and the open corbula afford good diagnostic characters. The spur- 
like nematophores at the base of the cost are well developed. 
A comparison of the open corbula of Aglaophenia attenuata with the proper Lytocarpal 
phylactocarp, as, for example, that of Lytocarpus myriophyllum, or of Lytocarpus racemi- 
ferus, and Acanthocladium huxleyc of the present Report will show that the mere fact of 
the coste not being adnate by their edges affords no sufficient ground for generic 
separation from Aglaophenia, more especially as in one species at least (Aglaophenia 
filicula, see p. 36) closed and open corbulz are borne by the same colony ; in Aglaophenia, 
however, the cost of the corbula, whether open or closed, are always more or less in the 
form of flat serrated leaflets, without hydrothece: or other appendages; while in such 
open forms of phylactocarp as occur in the genera Lytocarpus and Acanthocladium the 
coste are either long, curved, rod-like or sabre-shaped appendages, each carrying a 
hydrotheca, or are in the form of a series of strong spines without hydrotheca, or are 
simply replaced by a series of large nematophores. 
Dredged in Simon’s Bay, Cape of Good Hope ; depth, 10-20 fathoms. 
Aglaophenia acacia, n. sp. (PI. XII. figs. 1-4). 
Trophosome.—Colony attaining a height of about six imches ; stem monosiphonic, 
pinnately branched, branches opposite or sub-opposite, rather distant, carrying the hydro- 
eladia, which are about two-tenths of an inch in length, and are also borne by the main 
stem in the intervals of the branches. Hydrothecze deep, with deeply serrated margin. 
intrathecal ridge very short, situated just above the fundus of the hydrotheca ; mesial 
nematophore adnate to the wall of the hydrotheca for about one-half their height, and 
then terminating as a free short spine which does not reach the level of the hydrotheea 
margin ; lateral nematophores stout, slightly overtopping the margin. 
Gonosome.—Corbule rather short and deep, with about six pairs of closely adnate 
costee. 
The habit of Aglaophenia acacia is somewhat loose and spreading. The main stems 
continue unbranched for four or five inches from the root, and then give off opposite or 
nearly opposite branches, which confer on the species a very distinctive aspect. The dis- 
position of the primary branches is truly pinnate, while these again carry the pinnately 
disposed hydrocladia. The ramification is thus properly bipinnate, though the distances 
between the primary branches and between the hydrothecal ramuli give to it an aspect 
very different from that of Aglaophenia macgillivrayi, and of other bipinnate Plumu- 
lavide with their closely approximated branches and hydrocladia. 
Aglaophenia acacia is a deep-water species, having been dredged along with 
Aglaophenia filicula, at Station 75, July 2, 1873, lat. 38° 37’ N., long. 28° 30’ W.; 
depth, 450 fathoms ; bottom, sandy. 
