. Carnegie Institution of Washington publication. THAUMATOMETRA NUTRIX. 57 In the next stage represented (plate xxvm, figure 3) the radials have grown somewhat and assumed a triangular shape; the costal has appeared as a branching spicule. The anal plate lies wholly outside the radial mid- line; it has hardly any influence upon the shape of the adjoining radial plate in this stage. The stalk-joints can not be discerned in the upper part of the stalk; the lower ones are assuming their final shape. In the following stage (plate xxvm, figure 4) the arms have begun to form; the radials are joining
. Carnegie Institution of Washington publication. THAUMATOMETRA NUTRIX. 57 In the next stage represented (plate xxvm, figure 3) the radials have grown somewhat and assumed a triangular shape; the costal has appeared as a branching spicule. The anal plate lies wholly outside the radial mid- line; it has hardly any influence upon the shape of the adjoining radial plate in this stage. The stalk-joints can not be discerned in the upper part of the stalk; the lower ones are assuming their final shape. In the following stage (plate xxvm, figure 4) the arms have begun to form; the radials are joining, thus separating the basals from the orals. The anal plate is still small, but the radial to the right of it is now considerably in- fluenced by it (text-figure 8); a naked space, only partly occupied by the anal plate, separates it from the adjoining radial plate to the left. Also the adjoining oral plate has undergone some absorption. The costals are long and narrow, the original spicule still being discernible in the middle. The axil- laries are somewhat shorter ; along their outer edges the arm-joints have begun to appear in the typical shape of a spicule lying transversely and sending out prolonga- tions proximally and distally. The upper stalk-joints are still indistinctly separated from one another. A slightly more advanced stage is that figured in plate xxvm, figure 5. The arms have grown considerably, about 6 joints having developed. The axillary has assumed its typical shape with two oblique outer edges. The primary spicule is still dis- tinct, both in the axillary and the costal. The stalk-joints are now assuming their final shape also in the upper part of the stalk. There are still only 11 joints, the same number that was found in the youngest specimen. The last stage found is that represented in plate xxvm, figure 6. Unfor- tunately not one of these specimens is in good condition, the arms being broken off more or less completely. The first pinnule has appeared; i
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