INVESTIGATION OF FAUNA AND FLORA OF TRIAS OF BRITISH ISLES. 167 
to bottom, and it probably only needs careful search to extend its range 
in the British rocks. 
Until recently Lstheria minuta, var. Brodieana was considered as 
characteristic of the Rheetic. It occurs in a certain zone of this series in 
Gloucestershire, Worcestershire, Warwickshire, Somersetshire, and Moray- 
shire, and is so plentiful that it has been described as forming thin 
limestones. 
However, in 1900 several specimens, identified by Professor Rupert 
Jones, were found in the Keuper marls at Oxton, Cheshire,’ and its range 
has thus been extended into the Keuper proper. 
Habitat of Recent Estheria. 
More than twenty species are known to exist at the present time. 
We find them in freshwater pools, Strasburg ; brackish water marshes, 
Arzeu, near Oran, Africa ; in ditches filled with rainwater, Toulouse, 
Tunis, and Algeria; in freshwater marshes of the Island of Dahalac, 
on the coast of Abyssinia ; in stagnant water on the banks of the Tigris, 
near Bagdad ; in rainwater pools, Malta ; in freshwater streams near 
Nagpur, India ; in rainwater pools on limestone near Jerusalem, dry for 
ten or eleven months in the year ; in a dried-up ‘ vley’ near Port Elizabeth, 
South Africa ; in brackish water in Cuba and Cape of Good Hope, and 
in Lake Winnipeg. 
One species, Estheria Giboni, from a freshwater pool of Gibon, 
Jerusalem, was reared in England by Mr. H. Denny and Dr. Baird from 
the dry mud brought from the Pool of Gibon, 
Thus we see that the genus has a wide distribution ; it lives in fresh, 
stagnant, or brackish water ; it is capable of existing under great extremes 
of heat and cold, and in regions subject to great desiccation. 
According to Professor Rupert Jones, recent Hstherie appear, as it were, 
suddenly (like the Apus) in pools and ditches, and are quickly developed 
in tanks and ponds dry for even ten or eleven months in the year. 
Habitat of Fossil Estherie. 
Fossil Estheris have been found in the Old Red formation, and in 
almost every subsequent freshwater deposit up to the present day. 
They are constantly associated with other freshwater crustacea, fresh- 
water molluscs, fishes, reptiles, insects, and plants. Occasionally dwarfed 
marine shells are found, indicative of brackish conditions. 
No truly marine organisms have ever been found associated with them 
in the same bed. 
Dealing specially with Estheria minuta, we find it to occur principaily 
in the so-called marls and clays of the Trias series, and less frequently in 
sandstone. 
Professor Rupert Jones? remarks that the Estherie of the Keuper 
might have been at once regarded as of equally freshwater habits with 
their recent congeners were it not that the salt condition of the waters 
depositing much of the Keuper sandstones and shales is proved by the 
masses of rock-salt and by the casts of the cubical crystals of salt occurring 
1 Lomas, ‘ On the Occurrence of Estheria and Plant Remains in the Keuper Marls 
at Oxtor, Birkenhead.’ Proc. Liverpool Geol. Soc., 1901, p. 77, Pl. IV. 
2 Monoqg. Pale. Soc., 1862, p. 65. 
