89 
cular appearance. It was easy enough to catch numbers of them with 
a hånd net; for the approaching net they were springing away, 
just as if they were a swarm of insects, to other rocks or down 
into the water, where they were then very rapidly swimming or skip- 
ping over to some other rock. Upon the whole, this little Blennioid 
recalls Periophthalmus in its appearance and habits, a most pro- 
nounced parallel biological adaptation within two different families. 
In the black volcanic sand forming the beach on the Hast Coast 
of Krakatau I was very pleased in finding numbers of a small Spionid 
living in exactly the same way as described by me for Scole- 
colepis squamata from the Dutch and Danish sand beaches^). The 
worm sits vertically, free in the sand, not in tubes; when the smooth 
water glides down over the beach after the retreating waves, it 
raises its head above the sand, spreading its two long tentacles in 
two curves against the current, evidently with the object of catch- 
ing any small organisms that are carried down with the water. On the 
black sand they were very distinctly and much more easily seen 
than is Scolecolepis squamata on the white sand of our own 
beaches. The two curves of the tentacles remained quite distinet 
in the dry sand, after the water had run down. I was the more 
pleased to find this interesting worm here, as I had been looking, 
for it in many other places, but always in vain. The reason for 
its not oceurring on beaches of usual coral sand evidently is this 
that the sand is not uniform enough for it. Even if it looks very 
pure and uniform on the surface, it is very often full of larger or 
smaller pieces of coral farther down, and these larger pieces make 
the sand unsuitable for the worm. That the other animal forms, 
so eminently characteristic of such sandy beaches, were likewise 
represented here need scarcely be said. I would only mention 
the interesting faet that the Hippa’s found here were almost black 
as the colour of the sand — though, apparently, not specifically 
different from the white Hippa found so commonly on the sandy 
shores in these regions. 
1) Th. Mortensen. Biologiske Studier over Sandstrandsfauna’en, særlig 
ved de danske Kyster. Vid. Medd. Dansk Naturh. Forening, København 
Bd. 74. 1922. 
