Meretrix casta (Chemnitz) occurring in three stations of Veilar Estuary at Paranglpettai (S. India) was studied from April '75 to June '76 and at station I, the maximum number of 1077 dams/m² occurred in June '75 while the maximum was in May '75 at stations II and III which recorded respectively, 1312 and 1104 clams/m² Minimum number of 11 clams/m' was recorded in Septemlser '75 and February '76 at station I while the minimum nimiber of clams occurred in March '76 at stations II and III which recorded 80 and 5 clams/m² respectively.

Highest biomass values by weight were 2978.773 gm/m² for 768 clams in August '75 at station I, 3919.067 gm/m² for 693 clams in December '75 at station II and 628.907 gm/m²  for 389 clams in September '75 at station III. Lowest biomass values recorded were 2.053 gm/m' for 571 clams in station I, 6.635 gm/m² for 1109 clams at station II and 0.949 gm/m² for 405 clams at station III.

Clam population in station II was always more than in station I and III. Sediment analysis revealed that station I was sandy and station II was sandy-silt while station II was sandy-silt-clay with an increase in silt clay contents.