Between 450 and 1000 AD, seashells played a fundamental role in the socioeconomic and cultural dynamics of the populations living in the region of the Sayula Basin. The study of the exploitation of marine resources used to manufacture seashell adornments provides new data stemming from the large number of technical products. Mas has here carried out a detailed and systematic description of the malacological remains, from three analytical perspectives: taxonomic, typological and technological. The book includes a description of adornments’ technical traces, based on macroscopic, microscopic and micrographic observations (using a Scanning Electron Microscope) which is complemented with experimental protocols. The work establishes a model for the classification of each artifact according to its degree of transformation (such as blank, roughout, preform, debris, finished object, etc.) and thus determines its place in the operational sequence (the treatment of the raw material, the débitage, the shaping, and the finishing process). This research offers insights into the behaviour of pre-Hispanic craftsmen, and contributes towards an understanding of the mechanisms of past economies.