BIO 203



The Helicodiscus parallelus is a terrestrial Gastropod of the subclass Pulmonata, which is distinguishable by the use of pneumatostomes, openings used to take in oxygen.  Pulmates have lost their anscestral gill and the mantel now serves as a large lung (Nordsieck, R.).
Also, the Compound Coil has no visible eyes/eyespots.  This is because of the snail's subterranean habitat, where there is no advantage to having a sense of sight.  They spend the majority of their time within the thin splits of damp, rotting wood, this is likely why the operculum is at such an aggressive angle, to allow for easier movement and feeding (Pisbry, 1890).