Crassispira cerithina (Anton, 1838) is a common shallow water conoidean gastropod species, broadly distributed throughout the Indo-West Pacific. It has a distinctive shell morphology and has been referred to in many publications. It is also the first species of its family to have been studied from the viewpoint of toxinology. However, our molecular phylogenetic analysis based on fragments of the COI and 28S rRNA genes reveals the existence of two closely related distinct species, one of which is described as new (C. scala n. sp.). These two species are sympatric in several regions of the Indo-Pacific-in the Philippines, Papua New Guinea, Vanuatu and New Caledonia. They can be reliably distinguished by shell morphology and thus cannot be considered truly cryptic species. The radula is very similar in both species and does not permit species delimitation. A conchological reappraisal of further material similar to C. cerithina allows us to recognize two additional species, which are described as new (C. procera n. sp. from the Coral Sea and Philippines, and C. aurea n. sp. from Tahiti). These results demonstrate that even 'well-known' and seemingly well defined species may be species complexes and that molecular techniques should be routinely applied to confirm specimen identification, especially as part of resource-consuming studies, such as toxinology.