Conchological Variability of Anadara inaequivalvis (Bivalvia, Arcidae) in the Black-Azov Sea Basin. Anistratenko, V. V., Anistratenko, O. Yu., Khaliman, I. A. - An alien species in the Black Sea and the Sea of Azov - Anadara inaequivalvis (Bruguiere, 1789) - was recently discovered to have a wide range of shell variability. From the investigated samples (over 900 valves) six basic types of the shell commissural opening were defined; they are not, however, discrete conditions. Th e presence of intermediate variants reveals a gradual (continuous) character of the shell variability and indicates that all the samples investigated belong to the same species. Th e variation of some other Anadara characteristics is also discussed, including: quantity and ornamentation of the ribs on the surface of the valves, quantity of chevrons on the ligament area, shape of the hinge plate and quantity of hinge teeth. A comparison of conchological characteristics of Anadara from the Black-Azov Sea Basin with A. inaequivalvis from southeast India shows that ranges and patterns of shell variability of Azov-Black Sea Anadara correspond to variability of A. inaequivalvis from this species type locality - Coromandel Coast of India.