REPORT ON THE HYDROEDA. 
31 
extent as to render necessary a revision of the group by a more stringent limitation of 
Lafo'ea. See below, p. 32. 
The genus Halisiphonia is represented in the Challenger collection by a single 
species, which presents many points of special interest. 
Hcilisiphonia megalotheca , n. sp. (PI. XVI. figs. 1, la). 
Trophosome . — Hyclrocaulus a creeping and adherent tube which supports at irregular 
intervals pedunculated hydro thecae. Hydrothecae very large, cylindrical, gradually 
passing below into the long, smooth, cylindrical peduncle. 
Gonosome . — Gonangia spatuliform, borne on short peduncles and with the summit 
opening by a long, narrow, transverse slit. 
Locality. — Station 1G0, south of Australia; lat. 42° 42' S., long. 134° 10' E.; depth, 
2600 fathoms. 
The very long tubular hydrothecae gradually passing into then' long peduncles 
confer on this remarkable species an aspect as striking as it is distinctive. The 
hydrothecae measure about one-tenth of an inch in length, and are borne on peduncles 
whose length is for the most part nearly the same. The creeping stolon from which 
they spring twines in irregular contortions round the body to which it has attached 
itself. The deep cylindrical hydrotheca begins, at about three-fourths of its height 
from the margin, to taper into the peduncle, with the cavity of which its own is uninter- 
ruptedly continuous, so that it is not easy to say where the one ends and the other begins. 
The gonangia are, like the hydrothecse, borne by the creeping stolon-like hydrocaulus. 
Their form is remarkable. They are much compressed, so as to present a spatuliform 
shape, widening upwards, and gradually narrowing into a short peduncle below. They 
are widest at the summit, where they terminate in a sharp edge. Along this edge the 
walls of the gonangium admit of being separated from one another so as to bring into 
view a narrow slit through which the contents of the gonangium may be liberated. The 
appearance, indeed, of the gonangium with its slit-like opening is such as to suggest 
rather forcibly that of a fiat bivalve shell, or the ovarian nidus of certain Gasteropodous 
Mollusca. Nothing can be asserted of its contents, which had in every case disappeared. 
The collection contains but a single and somewhat fragmentary specimen, which 
twined round a portion of a fascicled stem, probably that of Cryptolaria abyssicola, a 
species with which it was associated. 
The enormous depth of 2600 fathoms from which both Halisiphonia megalotheca and 
Cryptolaria abyssicola were obtained has much significance, in connection with the fact 
that in both species the gonangia are present, Halisiphonia megalotheca affording the 
only known instance, and Cryptolaria abyssicola one of the very few, in which any 
part of the gonosome has been observed in these genera. 
