Preliminary note on variation of protoconchae of Clio pyramidata (Linnaeus, 1767) (Mollusca, Pteropoda)

A new method for the use of infraspecific variation in the characterization of watermasses in the past is indicated. The various formae of the thecosomatous pteropod Clio pyramidata can be distinguished by the size of their protoconch. Since in marine sediments these protoconchae are usually the most intact part of the pteropod shells, they can be used to trace the distribution of the formae in the past, and thus of the watermasses of which these are characteristic.