. Bulletins of American paleontology. North American Mitrate Stylophorans: Parsley 25 following detailed discussion on the morphology of the genus. The new information comes from: (1) restudy of the hitherto poorly-known Edenian forms; (2) new artic- ulated Cincinnatian specimens; and (3) several thou- sand disarticulated plates of Enoploura now in the Uni- versity of Cincinnati Museum. Theca.— Severa] important aspects of thecal mor- phology have hitherto been unknown or have not been discussed in the literature. The distal margin of many mitrates, including Enoploura, is commonly not pre- se
. Bulletins of American paleontology. North American Mitrate Stylophorans: Parsley 25 following detailed discussion on the morphology of the genus. The new information comes from: (1) restudy of the hitherto poorly-known Edenian forms; (2) new artic- ulated Cincinnatian specimens; and (3) several thou- sand disarticulated plates of Enoploura now in the Uni- versity of Cincinnati Museum. Theca.— Severa] important aspects of thecal mor- phology have hitherto been unknown or have not been discussed in the literature. The distal margin of many mitrates, including Enoploura, is commonly not pre- served, or is badly crushed and incomplete. With the exception of several Edenian specimens [figured by Bassler (1932, pi. 18, fig. 9), but the distal margins not discussed], all specimens previously illustrated in the literature fail to show the lower, distally-protuding, rounded lip of the distal marginals m5, m6, m'S. The lip extends from the upper portion of the transverse ridge, so that when one of these plates is viewed lat- erally, the lip is cantilevered above and out from the plastron surface. On m6, the lip portion of the plate is not as wide as the thecal portion at the transverse ridge, thereby creating slight gaps between m6 and mS/m'S. The lateral edges of the lip portion are slightly in- dented, but are parallel to the sagittal plane. The adjacent marginals m5 and m'S are also divided into thecal and lip portions, but not as distinctly, due to the lateral reduction in height and width of the trans- verse ridge. The shorter lip portion is angled toward the m6 lip and apparently in some individuals not only fills the indented portion of in6, but slightly underlies it as well (Text-figs. 10, 12C). The serrate transverse ridge developed on the inter- nal faces of the inferior distal marginals (PI. 5, figs. 1, 3, 10) is matched by a similar serrate ridge developed on the interior of at least three distal carapace marginal plates: CM2, CM3, CM'2. These opposed ridges f
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