160 ARTHUR WILLEY. 
at low water. The natives here call it “a pada ur-a-ta,” or 
simply “a ur-a-ta,’ which means “ the bones of the sea.” 
3. Nudibranchiata.—The Nudibranch molluscs, particu- 
larly the Doridide, are represented here by a great wealth of 
species of all sizes up to 60 mm. by 45 mm., many of them 
being brilliantly coloured. Their spiral egg-bands may be 
obtained without difficulty. Several species, including two 
Molids, have laid their eggs in my dishes. 
On the reef off Ralum, and in Blanche Bay too, there are 
to be found large numbers of very long spirally coiled ribbons, 
so thickly encrusted with sand that they appear to consist of 
nothing but sand. The natives call these ‘‘a pipia,” which 
means “‘ earth” or ‘“‘ ground.’ Some are tough and elastic, 
others brittle. ‘They are the egg-bands either of species of 
Doridide, or of other Opisthobranchiate Mollusca, but I have 
not yet been able to identify them. 
4. Onchidium.—One of the commonest Mollusca in the 
shallow water off the south-west shore of Rakaiya is a species 
of Onchidium. It is often found in the very heart of large 
friable stones, approximately at low-water mark, but some- 
times further out. It occurs in other parts of Blanche Bay as 
well. What service the dorsal eyes can be to it is not easy to 
imagine. Semper supposed it was to enable the Onchidium to 
perceive and escape from what he says is its chief enemy, 
Periophthalmus. But although I have seen a small species 
of Periophthalmus at Rakaiya, on the muddy shore of the so- 
called lagoon, it is difficult to accept Semper’s view. 
The papille which carry the eyes are obviously homologous 
with the retractile branched respiratory papille in the posterior 
dorsal region, and every transition can be observed between 
them. 
When kept in confinement in jars, Onchidium asserts its 
pulmonate qualities by often creeping out of the jars for long 
distances. 
5. Larve of Polygordius and Squilla.—It is worth 
recording the presence of larve of Polygordius in the “ Auf- 
trieb”” in Blanche Bay. In the narrow strait which separates 
