THERE can be little doubt that the not uncommon rhizopod identified by Hertwig and Lesser as above is indeed one and the same with Claparède and Lachmann's form, and, with not less doubt, is also identical with that erroneously called Amphizonella flava by Greeff.³ The test possesses ordinarily a hollow, dorsally convex discoid figure, somewhat like Arcella vulgaris, but a great deal smaller, its upper or convex side equally and evenly arched. Its colour at the middle is of a brownish yellow (resembling in tint that of the contents of many diatoms) mostly gradually fading off to the margins, which may be quite colourless; but I have myself frequently seen examples in which the change was abrupt and quite irregular. This colour resides in the test itself. The median portion of the test is thicker, and it gradually thins off to the margin. In many specimens an arcella-like facetting or punctate appearance can be readily made out, gradually disappearing towards the margin; but in many others this cannot be at all discovered when it has a more or less smooth, but not a glossy, aspect. I believe the appearance of "facetting" or "shagreening" is due to little rounded, closely posed, scattered scrobiculi.