The cult which is the subject of this paper centres round that magnificent snow-white gastropod shell called Chank by Europeans, sangu by the Tamil divers who fish it in the Gulf of Mannar,. and sankha by the people of Aryan speech in the north of India. To zoologists it is known as Xancus pyrum (L.), a name which replaces the former ones of Turbinella pyrmm and T. rapa. It is strangely local in distribution ; its main habitat is the sands between and around the rock-strewn pearl-banks of the Gulf of Mannar; here it thrives best, is most abundant, and grows to the largest size and most symmetric shape (FIG. I). Another centre where the same form is found is the northwest coast of Kathiawar but here its numbers are relatively few. A somewhat stunted variety or sub-species exists in Palk Bay and Strait and along the Coromandel Coast, with another in the Cape Comorin region, while one, sufficiently distinct to be given specific rank, occurs in the Andaman Islands. Nowhere outside of India is the chank found; neither in the Persian Gulf and the Red Sea, nor in Malayan and Australian waters does any closely related species occur.