63 
This fish is Plotosus anguillaris Bloch (Fig. 2), one of the 
Silurids. It has a long, pointed and barbed, erect spine in each 
pectoral fin and a similar one in the dorsal fin, provided with poi- 
son glands!). 
Alcock (Op. cit. p. 113) mentions another species of Plolosus, 
PI. arab, of the Indo-Pacific as a case of warning coloration, this 
species being, evidently, much more poisonous than PI. anguillaris. 
In this case it appears to be the coloration alone which makes the 
warning signal; there is no mention of a gregarious habit of this 
species. 
An instance of protective resemblance, no less admirable than 
the ,warning" of Plotosus, was observed in another species of fish in 
the same locality. At one place of the island there is a very small 
Mangrove, with a fine, sandy flat outside. Here were seen swimming 
among the floating old leaves of the Mangrove trees some small fishes, 
which looked so exactly like the leaves, that it was by no means 
easy to see which was a leaf and which a fish. The colour of the 
fish varies from yellow to dark brown, to suit the different shades 
of the leaves. Further the fish moves very gently, swimming now 
on the side, now erect, exactly like the leaves swaying with the 
gently moving water. : 
The fish is a species of the genus Platawx, probably Pl. teira 
(Forsk.); I can hardly doubt that also the other species of this 
Senus will prove to have the same habit, which may perhaps account 
for the great variability of these species. 
It is very interesting to see, how this resemblance with a leaf 
has been brought about. The greatly elongated and pointed dorsal 
and anal fins represent the stalk and the point of the leaf; the 
Very short, high, compressed body, the small, inconspicuous tail, 
and the remarkably rounded profile, give the outline of the leaf 
Very well, while the larger of the darker bands across the body 
represents the mid-rib of the leaf. From a figure alone it would 
Certainly not be possible to infer that this would be the habit of 
the fish — and, so far as I know, it has not been recorded in 
litterature, But on seeing the fish in its natural surroundings it is 
”) Pawlowsky. Uber den Bau der Giftdrisen bei Plotosus und anderen 
Fischen. Zool. Jahrbiicher. Abt. f. Anatomie. Bd. 38. 1914. p, 427. 
