. Bulletin - United States National Museum. Science. 216 BULLETIN 17, UNITED STATES NATIONAL, MUSEUM. oped at the end of a fold of the wall which in the most mature con- dition extends far into the zocecial cavity. The internal structure as exhibited in tangential sections has been discussed above and the septal folds of Nicholson shown to be the greatly infolded, zocecial wall bearing an acanthopore. Vertical sec- tions are especially interesting for the reason that they exhibit the diagnostic generic character—the zonal thickening of the walls accompanied by an accelerated development of aca
. Bulletin - United States National Museum. Science. 216 BULLETIN 17, UNITED STATES NATIONAL, MUSEUM. oped at the end of a fold of the wall which in the most mature con- dition extends far into the zocecial cavity. The internal structure as exhibited in tangential sections has been discussed above and the septal folds of Nicholson shown to be the greatly infolded, zocecial wall bearing an acanthopore. Vertical sec- tions are especially interesting for the reason that they exhibit the diagnostic generic character—the zonal thickening of the walls accompanied by an accelerated development of acanthopores. The characters of such a section, with two successive immature and mature zones, are shown in figure 118 a. Nicholson's vertical section. Fig. 118.—Stigmatella fookdh. a, vertical section, X20, passing through two layers of zooecia; &, SECTION, X20, WITH THE ZOCECIA SHADED; C, PORTION OF THE SAME SECTION, X35, "WITH FEW ACANTHOPORES; d, ANOTHER PORTION, X35, SHOWING AN EXTREME DEVELOPMENT OF THE IN- FOLDED ZOCECIAL wall; e, several ZOCECIA OF A TANGENTLiL SECTION, X50, WITH SMALL ACANTHOPORES PLAINLT DEVELOPED AT THE ENDS OF THE INFOLDED WALLS. KtTCKERS SHALE (02), BARON TOLL'S ESTATE, ESTHONIA. includes only the mature region of a single zone, but the tabulation of both sets of tubes is the same as in the original of figure 117 a. Without careful comparison, the zocecial characters of the present form seem almost identical with those of Stigmatella injiecta, but the zooecia of the latter are almost twice the diameter of the former. Internally the two species are quite distinct, especially in the tabula- tion. No American species with which either might be compared is known. Occurrence.—Rare in the Kuckers shale (C2), Baron Toll's estate, near Jewe, Esthonia. Plesiotype.—Csit. No. 57298, Section of figured specimen in the collections of the British Please note that these images are extracted from scanned page images that
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