Scaphopod shells usually have four layers, and these are used for identification. The shell is curved, tubular, and shaped like an elephant tusk. Most average 3 to 6 cm long, but can range from 4 mm to 15 cm. Fossils show specimens 30 cm long.
The scaphopod shell is open at both ends. The wider end of the shell where the head and foot extends out is the anterior end. The posterior is the narrow end of the shell which usually is at or below the substrate.
The shell surrounds a large mantle cavity, and wraps around the viscera to form a tube. The mantle cavity goes along ventral side to a smaller opening at the other end. No ctenidia are present, and gas exchange is through the mantle surface. Cilia an currents move water thorugh posterior aperature. Occasional muscular contractions expell water from the posterior end of the shell.
The head is a short, conical projection (probosicis) with a mouth. Lobes on each side of the head have threadlike tentacles, called captacula, which are used to capture food.
Other Physical Features: heterothermic ; homoiothermic; bilateral symmetry