64 
THE VOYAGE OF H.M.S. CHALLENGER. 
Gonosome. — Gonangia shortly pedunculate, borne by the pinnae, each from a point 
just below a bydrotbeca ; male gonangia urn-sbaped, crowned by a conical projection 
which carries the orifice on its summit, and is surrounded by four symmetrically disposed 
flattened spines ; female gonangia obovate, crowned by four spinous valves which enclose 
the marsupial chamber. 
Locality. — Station 75, near the Azores; lat. 38° 38' 0" N., long. 28° 28' 30" W.; 
depth, 450 fathoms. 
Though the specimens obtained by the Challenger differ somewhat from the 
Diphasia pinaster of the European seas, especially in their shorter and rather more 
rigid pinnae, and in the more elongated form of their female gonangia, I have little 
hesitation in referring them to this species. 
Diphasia pinaster is a well-marked species, and when the pinnae are laden with 
their large and elegantly formed gonangia constitutes a striking and beautiful object. 
The specimens obtained by the Challenger have a height of four or five inches. The 
hydrothecae are decidedly subopposite in the pinnae, but more nearly opposite in the 
stem. The orifice is oblique, having a wide sinus at its epicauline side and is provided 
with a thin membranous lid which is hinged on to the bottom of the marginal sinus. 
When depressed this lid lies within the orifice, and then stretches transversely across the 
cavity of the hydrotheca. No distinct joints are present in any part of the stem or pinnae. 
The male gonangium has the small circular orifice raised on the summit of a conical 
projection of the roof, and this is surrounded by four symmetrically placed strong 
spines, which are laterally compressed, and have their bases extended downwards as four 
keel-shaped ridges along the walls of the gonangium. 
The female gonangia with the marsupium are nearly twice the length of the male. 
The marsupial chamber is of about the same height as that of the gonangium proper. The 
four valves by which the marsupium is enclosed have a row of two or three strong spines 
extending along the mesial line of each. 
The specimens obtained by the Challenger were dredged from a depth of 450 fathoms, 
and form part of the rich Hydroid fauna which the region of the Azores has yielded to 
the dredge. 
Thuiaria, Fleming. 
Thuiaria, Fleming, British Animals, p. 545. 
Generic Character. Trophosome. — Colony dendritic ; hydrocaulus divided by well- 
marked joints at regular or irregular intervals into internodes, each of which carries 
many hydrothecse. Hydrothecse distichous, opposite or alternate, sessile, adnate by 
a greater or less extent of their walls to the hydrocaulus, margin of orifice entire or 
variously cleft or dentate. Hydranth with conical hypostome. 
