Abstract
In the course of my studies on the anatomy of certain of our western land-snails it early became evident that the species of the splendid genus Monadenia (Pilsbry) so far as investigated align themselves in two very distinct and apparently natural groups. These groups find their strongest characterization in the genitalia, but it has likewise been possible to discover support for them in certain features of the shell. For several years I have been putting off publication of my conclusions in the hope of fortifying them by an investigation of the animals of all or nearly all of the known species. This has as yet been only possible of attainment in part, but since no conflicting evidence has come to light in any of the species studied, and as I wish the privilege of reference to the situation in a taxonomic and distributional paper shortly to appear, it seems desirable to publish this preliminary synopsis.
