74 
THE VOYAGE OF H.M.S. CHALLENGER. 
cylindrical peduncle to which the hydrotheca-bearing portion is attached by a very 
oblique splint-like joint (fig. 2c). 
The hood-like roof which arches over the orifice of the hydrotheca is present in all 
the hydrotbecse, whether of the pinnae or of the stem, and consists of a very thin, trans- 
parent, chitinous membrane. So delicate is it that it is easily torn away, and it was 
only in some cases that it was sufficiently perfect to enable its form to be satisfactorily 
determined. 
The gonangia are beautiful objects and constitute a striking feature of the species'. 
They are relatively narrow, but have a length which is equal to about twice that of an 
internode of the stem. With their axis gently curved they gradually taper from a 
rounded base towards the terminal circular orifice. They are thickly set from base to 
summit with minute spines, whose points are directed towards the summit of the 
gonangium. When the stem is viewed in profile the gonangia, though strictly distichous 
in their origin, are seen to be for the most part directed with a secund disposition 
towards one side of the stem. 
The largest example of Desmoscyphus acanthocarpus in the collection measured 
about two inches in height. The species is a member of the rich Hydroid fauna occurring 
off the coast of Bahia. 
Hypopyxis, n. gen. 
Name from Wo, under, and Trusts, a box, in allusion to the cup-like appendages 'which lie below 
the hydrothecse. 
Generic Character. Trophosome. — Hydrocaulus divided by well-marked joints into 
internodes, each carrying numerous pairs of hydrothecse. Hydrothecse opposite, adnate 
to one another by their opposed sides, each having attached to its base two minute cup- 
shaped appendages. 
Gonosome . — Gonangia destitute of marsupium, springing from the hydrocaulus in 
the intervals of the pairs of hydrothecse. 
The genus Hypopyxis has in its opposite and connate hydrothecse close relations with 
Desmoscyphus. From Desmoscyphus , however, it is distinguished by the presence of the 
cup -like appendages at the base of the hydrothecse. 
That these appendages must be regarded as sarcothecse can scarcely be doubted, and 
Hypopyxis will thus afford an additional example of the very exceptional occurrence of 
these bodies in genera not referable to the Plumularinse. 
Hypopyxis labrosa, n. sp. (PI. XXXV. figs. 1, la). 
Trophosome. — Stem simple or very sparingly branched, monosiphonic, and set with 
pinnately disposed, alternate ramuli, which are divided by very oblique joints into 
