Sect. I. Coquilles univalves.

Gen. 1. Le limax, cochlea. Quatre tentacules, dont deux plus grands portent des yeux à leur extrémité. Coquille univalve en spirale. IX. The system of Muller first published in 1773, and afterwards extended in a different work which appeared in 1776, arranges testacean animals into three families. The following is a view of this arrangement taken from the latter work on the zoology of Denmark and Norway.