12 



conditions now existing in more or less land-locked bays which 

 are not true backwaters, e.g., Tarnpalakam bay in Ceylon, Tuti- 

 corin bay in South India — it would appear that when the earlier 

 deposits containing Gardium, Dolium, and. Fusus were forming, 

 the area now occupied by the lake and by much of the low 

 land to the west was part of the open sea. Shallow water 

 conditions prevailed and the appearances indicate that deltaic 

 deposits of great extent were contemporaneously in course of 

 formation. By the drifting of this sand and silt along the 

 coast by monsoon action, northwards most probably, a long 

 sand spit, gradually extending and growing, would tend to 

 form, creating such a partially protected bay as we now see 

 at Tuticorin, but of vastly greater extent. This open bay 

 condition may be termed the second stage in the lake's history. 

 For a long period, as counted by years, little change took place 

 in the fauna ; Cardium, Fusus, Dolittm, Sanguisorba, Turlinella 

 (chank) and other shallow water marine molluscs lived on in 

 the sands, cockle beds being particularly well populated. By 

 degrees as the protecting spit grew in length and strength, it 

 gave greater quietude to the waters of the bay ; silt instead 

 of being carried to the deeps settled in increasing quantity in 

 the bay and cockles and other sand-bank animals began to find 

 their environment increasingly unfavourable and gradually 

 died off. By this time the bay had become more or less 

 landlocked by the extension of the natural breakwater formed 

 by the spit, and this stage, characterised by muddy bottom 

 and as yet an unimpeded tidal condition of its waters, is the 

 third in the history of the lake. It was at this period that 

 Placuna supplanted Cardium and other sandy bottom molluscs. 

 It may have been towards the close of this phase that the 

 Dutch settled at Pulicat as the town now nearly a mile inland 

 is said to have been situated on the sea coast in Dutch times 

 (J. H. Taylor in G.O., No. 293, dated 7th June 1883). 



The present condition of the lake represents the penultimate 

 stage characterised by the reduction of the depth of the lake 

 to a condition of extreme shallowness and the virtual blocking 

 out of free tidal flow. The landlocked bay has become a lake 

 liable to be closed for months to the sea, subject to extreme 

 differences of level due on the one hand to excessive evaporation 

 over an extensive shallow area and on the other to the accession 

 of enormous volumes of flood water unable to drain away 

 unless they burst a way through the weakest part of the sand 

 embankment which impounds the waters of the lake. The 

 reduction in salinity caused periodically by these floods has 

 made the lake unsuitable for the continued well-being of 

 Phcu?ia ) so the beginning of this stage witnessed the virtual 



