24 
when young. The lid is triangular in shape and thick but small; it may bear nematophores. 
The ampullae appear as slight swellings at the base of the lid: their surface is smooth. These 
ampullae were female: no males were found. 
There are some points of resemblance between this species and the imperfectly described 
Endohelia japonica of Mitre Epwarps and Haine, but in the present state of knowledge we 
think it advisable to keep the Siboga species distinct. 
The species may be defined; 
Hydrophytum subflabellate, branches occasionally anastomosing; large nematophores on 
stem and lid; lid small, thick, triangular; ampullae at base of lid. 
Two fragments, dry. 
This is a partially encrusting species. It is subflabellate and the branches of the small 
specimens at our disposal do not show any signs of anastomosis. The colour is yellowish white. 
The surface is marked by pronounced longitudinal and fine transverse striations and bears a 
few scattered, small nematophores, situated in pits with slightly raised edges. The cyclosystems 
are round and in a young colony their average diameter is 1,2 mm. and in an old one 1,6 mm. 
The edge of the cyclosystem is exsert and deeply crenate. The lid is small, narrow and thin, 
the two sides slightly reflected upwards. The lid has the appearance of having been formed 
from only one septum, not from several, as seems to be the case when there is a broader 
base. It also appears in this species to be a comparatively new formation, the septum which 
forms the lid, projecting as far towards the centre of the gastropore as the other septa. When 
the lid is broken off, the lid septum can only be distinguished from the others by being rather 
thicker. At the base of the septa of young cyclosystems, there may be nematophores, similar 
to those described by Mosetry in the same genus. The calicles are from 1,2 to 1,6 mm. apart. 
The ampullae are represented in the specimens from Stat. 226 by a swelling running all round 
the cyclosystem or on the two lateral sides only and causing in the latter case considerable 
distortion of their usual form. This swelling contains small cavities and is consequently probably 
a male (Fig. 32). Unfortunately the only specimens showing this kind of ampullae were dried 
and further information as to their structure could not be obtained. One cyclosystem only in 
the small colony from Stat. 177, showed a young ampulla behind the cyclosystem, this was 
probably a female (Fig. 31). 
This species is allied to C. éaéza in the size of the lid and encrusting method of growth. 
In C. éalza however the lid is much more massive and bears the characteristic, large nema- 
tophores. The nematophores are much smaller in C. stexofoma. The edge of the cyclosystem in 
C. stenopoma is much more deeply crenate, whereas in C. dala the edges of the old cyclo- 
systems are not crenate at all. Though the female ampullae are situated behind the cyclosystem 
in both species, their appearance is different, those of C. dada being scarcely noticeable on 
the surface. Until further evidence is obtained the two species may be considered distinct. 
