Without careful study the differences between the forms of Inella are hardly noticeable. When examined under a high power it is soon found that species which to the naked eye appear very similar or hardly distinguishable are really characterized by quite a different method in their sculpture, though the general result may be not very dissimilar in its salient features. The tubercles of one are due to grooves cutting transverse riblets; of another, to spiral ridges rising to nodules on the riblets ; of a third, to rows of nodules side by side without spiral or transverse sculpture of any kind. Inella forms have been separated after several days' close study from an assembly which the first examination had almost decided to place in the category under one specific name, However, there are distinct definable differences between them, and the fact that the microscope is required to perceive these differences should have no effect on our estimate of their systematic value.