ABSTRACT
The two neozelanic species Struthiolaria papulosa and Pelicaria vermis have been studied as regards ecology, feeding mechanism, and structure and function of the digestive system. They are dwellers on sand or sand-mud-flat, with a feeding position just below the surface, where they construct paired siphonal tubes with the rostrum. A ciliary mode of feeding has been acquired by the modification of the gill filaments and the pallial rejection system. The alimentary canal is adapted for deposit feeding and has developed a crystalline style. Food particles are conducted to the stomach by a functionally reduced mucus-secreting oesophagus, where they are subjected to the action of the rotating style, and a complex system of ciliary currents. Digestible particles are passed into paired diverticula, where absorption and intracellular digestion. takes place, while faecal material is surrounded with mucus and formed into firm pellets by the ciliary and muscular action of the intestine. The relationships of the Struthiolariidae are discussed, and their origin from the Aporrhaidae is postulated.
