Nassarius fossatus, the channeled basket snail, is a species of sea snail, a marine gastropod mollusk in the family Nassariidae, the Nassa mud snails or dog whelks. It is native to the west coast of North America where it is found on mudflats on the foreshore and on sand and mud in shallow water.
Nassarius fossatus is a predator and scavenger. When the tide is out it crawls across the surface of the mud leaving a distinctive trail. It is able to detect odors with its long proboscis and when it finds something edible, it winds its foot round it and rasps at the surface with its radula. A dead fish in a creek has been found to attract snails from as far away as 30 m (98 ft) downstream. N. fossatus can similarly detect the approach of a predator such as the starfish Pisaster brevispinus. Its reaction is either to crawl away rapidly, rocking its shell from side to side, or do a spectacular flip or series of flips, catapulting itself with its muscular foot.
Nassarius fossatus lays its eggs on eelgrass or some other solid object on the surface of the mudflats. First it cleans a portion of leaf blade with its radula, then it forms a fold in its foot connecting its genital pore with its mucous pedal gland. The egg mass passes along this fold and the pedal gland is used to cement the egg capsule to the leaf blade. This process takes about ten minutes, during which time the snail’s body and shell oscillate from side to side. After this, the snail moves forward slightly and repeats the process, eventually producing a series of flattened capsules that overlap each other giving a shingled effect. A typical egg string may contain 45 eggs and be 6 cm (2.4 in) long