Turbinella pyrum (Linnaeus, 1767) and T. rapa (= Turbinella pyrum var. acuta Hornell, 1916 are different species. These two species are very common along Tamil Coast. I too collected few specimens.
You may refer
1. Variation in Shell Morphology and Adult Specimen Weight in Three Varieties of a Commercially Important Gastropod Turbinella Pyrum (Linnaeus, 1767) From Southeast Coast of India. Sabapathi Arularasan, Viswanathan MS , Venmathi Maran BA , Galib Uz Zaman and Chandra Shekar M. Arularasan et al., J Marine Sci Res Dev 2016.
2. Haplotype variation and phylogenetic analyses of three commercially important morphological variants of genus Turbinella from the southeast coast of India based on the 16S rRNA gene. Sabapathi Arularasan, Neelam M Nathani, Venmathi Maran BA, Ramesh K Kothari, Chandra Shekar Mootapally. Sabapathi Arularasan. Bull Mar Sci. 93(4):000–000. 2017