Upper Pennsylvanian Gastropods from Kansas

Abstract

A molluscan fauna collected in north-central Kansas from the Deer Creek limestone of the Shawnee group, upper Pennsylvanian (Virgil) in age, contains bellerophontid and other gastropods that excellently show apertural characters and some features of shell structure.
Study of specimens of Euphemites indicates that the prismatic shell layer, secreted by an anterior border region of the mantle, is marked on the outerside by growth lines and covered externally by a thin smooth shell layer, here named perinductura, formed by a backward reflection of the outer edge of the mantle and partly by a longitudinally ribbed inductura deposited by the posterior and lateral parts of the mantle. Some species of Euphemites show the presence of another distinct shell layer that is deposited over part of the inductura. This layer is named the coinductura. The “obsolescence” of revolving ridges on a portion of the last whorl of Euphemites, not previously well explained, is seen to belong inherently both to old and young individuals.
The smooth area is covered only the noncostate perinductura, whereas the costate area is formed by the inductura or by the inductura and coinductura. A new bellerophontid genus, Knightites, which is represented in the collections by nearly all growth stages, is especially characterized by a series of paired tubular projections bordering the slit band. These hornlike structures are believed to mark the loci of incurrent streams of water that bathed the ctenidia and osphradia. Mature or gerontic specimens of this genus and of
some other bellerophontids in the collection show a thick inductura that is much more strongly curved transversely than the underlying shell of the preceding whorl. A new species that is assigned to Warthia, previously known from Permian rocks of Asia, seems to be the first determination of the occurrence of this genus in North America. Two new species of Bellerophon are described.