... of the Early/Middle Ordovician marine gastropod assemblage in the studied region; Teiichispira argentina (Kayser), previously known from the San Juan Formation, is described with a complete teleoconch and associated operculum. The opercula of both Teiichispira species are complete and preserved in life...

...David M. Rohr; Gregory P. Wahlman Abstract A single specimen of Oriostoma globosum (von Schlotheim, 1820 ) from the Silurian-age (Wenlockian) Laurel Limestone in southeastern Indiana preserves a partial, multispiral operculum in situ within the aperture. Only eight specimens of in situ Oriostoma...

..., indicating a different preservation potential of shells and opercula, as the calcitic operculum is more robust than the aragonitic shell. In contrast to previous arguments that most shellbeds in the Turkana Basin sequence represent undisturbed life assemblages, a taphonomic bias is clearly evident reducing...

... as seen in Otostoma is unknown in modern neritids, which usually are either smooth or spirally sculptured. Here we describe the operculum of Otostoma retzii ( Nilsson, 1827 ) for the first time; it closely resembles that of Nerita and many species of Neritina Lamarck, 1816 , yet differs...

...DAVID M. ROHR; MICHAEL F. FIX; GUY DARROUGH Ceratopea unguis is the youngest and most common species of the genus and its operculum expresses the greatest variability ( Yochelson and Bridge, 1957 ). Other shells (not opercula) assigned to the genus include Ceratopea buttsi Yochelson...

...DAVID M. ROHR; JIRI FRYDA 06 11 2000 The Paleontological Society 2001 F ossilized opercula are uncommon in Paleozoic rocks, and shells with the operculum in place are rare. A single specimen with the operculum in place was discovered by P. Slehofer in a concretion...

...David M. Rohr; Ellis L. Yochelson Abstract The only two known life associations of the shell and operculum of Maclurites Le Sueur, 1818, are described for the first time. Maclurites cf. magnus Le Sueur, 1818, from the Middle Ordovician of Alaska demonstrates that the operculum fits slightly inside...

...Ellis L. Yochelson Abstract An operculum of Maclurites , first described by Billings in 1865, is redescribed from the original material collected at Cape Norman, northwestern Newfoundland, and from additional specimens from Ellesmere Island, Canadian Arctic. Based on indirect evidence, a very late...

... in the Lower Silurian (Llandoverian) of Quebec permits documentation of their variation and ontogeny. Comparisons of these opercula with previously reported specimens from Gotland indicate that the operculum of Oriostoma can be distinguished by its unique sculpture. The exterior surface of Oriostoma has...

...Ellis L. Yochelson Abstract An operculum associated with Helicotoma is described from the Middle Ordovician Tyrone Limestone of Kentucky. If assignment to this genus is correct, it suggests that the Euomphalacea and the Oriostomatacea are distinct lineages. GeoRef, Copyright 2004, American...

...Ellis Leon Yochelson Abstract A reexamination of Hyolithes carinatus Matthew from the Middle Cambrian Burgess shale [of British Columbia] has shown that the features considered by C.D. Walcott to be supports for the fins of pteropods actually appear to be outgrowths of the operculum. If the dorsal...