GENERAL CHARACTERISTICS OF MOLLUSCA
- Body is short and partially or wholly enclosed by a fleshy outgrowth of the body wall called mantle.
- A shell if present secreted by the mantle and of one, two or eight parts.
- Head and ventral muscular foot closely allied with foot variously modified for crawling, burrowing , swimming, or foot capture.
- Digestive system complete, complex, with ciliary tracts for sorting small particles, mouth with radula bearing transverse rows of minute chitinous teeth, anus opening in mantle cavity.
- Circulatory is open type.
- Respiration by ctenidia (gills).
- Nervous system typically a circumesophageal nerve ring with various pairs of ganglia and two pairs of nerve cords.
- Sexes usually separated