In the interradii the marginal lamella undergoes modifications due to the fact that the bases of the pedalia are situated a little upwards from the exact margin, and that the lamella follows the outline of the bases. Fig. 1 shows one of the interradial corners of the bell margin looked at directly from the surface, so that the curved outline of the junction of the base of the pedalium with the exumbrella is seen. The trace made by the lamella where it meets the surface ectoderm follows this outline. The lamella is also shown in the vertical section through the interradius (Fig. 5 or 20, _vlm_), where it is seen running from the connecting canals (_cc_), which joins the two adjacent marginal pockets, upwards and outwards to meet the surface ectoderm. Its course from canal to surface is not in a direct line, but curved with the concavity upwards. Hence, in cross-sections at certain levels through the interradial corner it is met more than once and gives rise to appearances that seem at first sight too complicated for it to be just the same structure as the simple marginal lamella described above. That it is the same, and that the complication is only due to the insertion of the pedalia above the margin, can be determined by following through a series of cross-sections, the essential ones of which, as I hope, are given in Figs. 40-43. The levels of these are shown on Fig. 5 by the letters _w_, _x_, _y_ and _z_, respectively. Fig. 40 shows the lamella cut but once, just below its highest part. The section is above the level of the connecting canal and hence still shows the vertical interradial lamella _ivl_. Fig. 41, at the next lower level (_x_), shows the same portion of the lamella intersected a little nearer the interior, while the junction with the endoderm of the connecting canal is shown still further inside. Fig. 42 is at level _y_, just through the bend of the loop, so that in part of its course the lamella is cut almost horizontally, _i. e._ in its own plane. Fig. 43 finally shows the lamella as it appears below the level of the connecting canal, cut twice, each portion joining endoderm of marginal pocket with ectoderm of surface. It thus bears exactly the same relations that it had when we first met it in Fig. 38 (_vlm_), except that here in Fig. 43 one finds that a cross-section cuts it at right angles instead of a vertical as in Fig. 38, as a result of its being pushed upwards from its former position on the margin by the insertion of the pedalium above the margin.