FOZ: | N. ANNANDALE: Fauna of Seistan. 243 
MARGINAL FAauNA. The marginal fauna is very scanty. It 
includes no molluscs, fish ot crustacea, and in winter we found no 
aquatic insects. The lower surfaces of blocks of clay, however, 
were covered with a fairly luxuriant growth of Ephydatia fluvia- 
tilts, in a different phase from that found in the reed-beds, and of 
Fredcricella sultana jordanica. ‘The latter were covered with Vorti- 
cellid Protozoa. Just above the water-level certain insects were 
not uncommon in the same position, notably the Tipulid Symplecta 
punctipennis, at least two species of Ephydrid flies, and a cricket 
(Achtea bimaculata) also found in a similar habitat on the shore of 
the Lake of Tiberias. 
COMPOSITION OF THE FAUNA AS A WHOLE. 
The composition of the aquatic fauna of Seistan cannot be 
described as abnormal, but there are certain deficiencies that call 
for discussion. Some of these are due to geographical cause, 
which will be discussed later, but others are not so easily explained 
and evidently depend on some factor in the environment nct yet 
elucidated. The most noteworthy are the apparent absence of 
Crustacea Amphipoda and of most families of aquatic Rhynchota. 
Freshwater Amphipods are scarce in the plains of India and asa 
ruie occur only in the large rivers, in which the species are im- 
migrants from the sea.!. At even moderately high altitudes in the 
Himalayas, however, species of Gammarus and Talorchestia occur 
and in the Quetta district of Baluchistan, between 5,000 and 6,000 
heetaralt least two species are abundant in every spring — stream. 
We could find none in Seistan. 
The absence of all aquatic Rhynchota except Notonectidac 
and Corixidae struck us very much in Seistan, particularly in 
reference to that of the surface-haunting Hydrometridae. It is of 
course possible that we failed to find these species in winter be- 
cause they were hibernating, but this is improbable for two rea- 
sons, fitstly, because we sought for them carefully in spots in 
which they might have been expected to conceal themselves had 
they left the water temporarily, and secondly, because they are not 
uncommon on the water at the same season in adjacent districts. 
Dr. Kemp found a Miucrovelia abundant on the Zanginawar 
I,akes in the eastern part of the Baluch desert in December, and 
I noted a Gerrzs on small streams near Peshawar in large numbers 
in January. In neither instance was the temperature higher than 
it was in Seistan in November and December. The line of vege- 
table debris that marks the flood level on the bare shores of the 
Hamun-i-Helmand would seem to be an ideal retreat for hiber- 
nating Hydrometridae and we found amongst the fragments of 
reeds, etc., two species of Reduviid Rhynchota, several species of 
Carabid and Staphylinid and one of Curculionid beetles, at least 
two species of Diptera, a cricket and an earwig, a wood- louse and a 
! Cf. Chilton, Rec. Ind. Mus. XIX, p. 79 (1920). 
