Note 125 — 8. Genus—CORONULA. Pl. 15, 16.

These should be counted on the under side of the shell, for if counted from the outside, the number would be thought to be twenty-four, as on the side of each compartment bordering the radius, a half-fold has the appearance of being a whole fold, so that in appearance six folds are added to the real number of the folds. This caution is necessary whatever the number of real folds may be, that is, whether or not the original eighteen folds have been increased by subsequent plications. These remarks, also, are applicable to the other species.