PIX ELL—POLYCHATA OF THE INDIAN OCEAN 83 
caleareous polyzoa. The pedicle of the operculum is very wide and has fringed lateral 
wings. Many of the specimens are larger than those described by Willey: one of the 
largest has the abdomen 17 mm. long, containmg 84 segments of greatest width 4mm. 
and the thorax 5mm. long and nearly the same in width. The branchiz (24 pairs) are 
4mm. high when extended, and the operculum very slightly higher. 
15. Spirobranchus semperi Mérch, var. aceros nov. 
This only seems to differ in having a flat opercular disc without horns, but very 
much overgrown with Hydrozoa—the yellow chitinous perisares forming branching 
processes 1mm. or more high in some places. Amongst these were found some small 
crustacea. The one specimen present has about the same dimensions as the specimen 
of Spirobranchus semperi quoted above, but is slightly more elongated owing to its 
having been preserved in its tube. 
Locality. Amirante Islands, F.I., 29 fathoms. 
This has been placed as a variety only because it seems possible for opercular spines 
not to develop in some cases. In one specimen of Spirobranchus contiert described below 
three-branched spines were present on the dorsal half of the plate, while the ventral 
was quite free from them. 
16. Sprrobranchus contier: (Gravier) (Plate 9, fig. 8). 
Pomatoceropsis contiert, Gravier (21) 1908. 
Specific characteristics: 1. Interbranchial membrane more or less fimbriated along 
its free edge. 2, Operculum with five (or six) much branched processes; pedicle winged. 
3. Uncini with nine or ten teeth only. 
This species seems to resemble closely Mérch’s S. dendropoma (87), for which, 
however, Benedict (8) describes processes on the outer part of the radioles themselves 
at the level of the interbranchial membrane. 
Localities. Numerous specimens “commensal with two species of coral from entrance 
to dock, Suez,” others from sandbanks, Chaki-chaki Bay, Pemba; also from Zanzibar and 
from Suakin Harbour, Red Sea, from divers. 
Tubes covered with layer of coral to near mouth. 
“ Branchiz yellow, green and white with long filiform tips, interbranchial membrane 
extends about half-way up. Body dark chocolate red, velvety in appearance, the thoracic 
membrane being dark green and yellowish. After being in alcohol some time a pink 
colour dissolves out and the bodies then appear dark blue.” 
The process inside the lateral lobe of the collar that Gravier refers to as the languet 
is distinctly a small lateral projection of the ventral lobe of the collar. It varies a good 
deal in shape and is very similar to that generally met with in the genus Spiro- 
branchus, being less definite in shape as a rule than the typical languet in Pomatoceros 
triqueter. 
The variation in these specimens is very marked. In most the five or six branching 
processes on the operculum are hidden by a more or less cone-shaped or spherical mass 
of debris which seems to be held together partly by these processes and partly by the 
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