. A dictionary of the fossils of Pennsylvania and neighboring states named in the reports and catalogues of the survey ... Paleontology. Plat. 672 Platyceras membranaceum, Ringueberg, Bull. Buffalo S. N. S., Vol. 5, 1886. Niagnra, VI. Platyceras mitelliforme, new species^ Simpson Trans. Amer. Phil. Soc. Philada. 1889, page 456, fig. 26, 1, side view, fig. 2, dorsal view. Shell small, obliquely arcuate from the base; apex incurved, making --^-^:l_j».j^ p^j.^ of one volution; below which the body volution rapidly increases in size. Width at the base equal to three-fourths the len
. A dictionary of the fossils of Pennsylvania and neighboring states named in the reports and catalogues of the survey ... Paleontology. Plat. 672 Platyceras membranaceum, Ringueberg, Bull. Buffalo S. N. S., Vol. 5, 1886. Niagnra, VI. Platyceras mitelliforme, new species^ Simpson Trans. Amer. Phil. Soc. Philada. 1889, page 456, fig. 26, 1, side view, fig. 2, dorsal view. Shell small, obliquely arcuate from the base; apex incurved, making --^-^:l_j».j^ p^j.^ of one volution; below which the body volution rapidly increases in size. Width at the base equal to three-fourths the length of the anterior side; length of the posterior side less than one-half of the anterior ; right and left sides equally developed. Anterior side convex, with a prominent, broad, rounded carina along the middle; on each side of the carina, towards the base, a shallow depression. On some of the specimens there are indications of very slight plications on the posterior side. Aperture oblique, broadly elliptical; peristome a little sinuous at the carina, and some- times slightly sinuous, corresponding with the faint folds of the posterior side. Surface marked by concentric lines and by broad undulations, which sometimes give to portions of the shell a lobed appearance. A specimen of about the average size measures as follows; Height 12 mm.; length of the ante- rior side 25 mm.; of the posterior 8 mm.; width at base 22 mm.; thickness 18 mm. The characteristic feature of this species is the prominent carina or elevation along the dorsum. It may be distinguished from Platyceras inequale of this for- mation by its somewhat larger size, the prominent carina, and the equal development of the right and left side; from Platy- ceras dor sale by its smaller size, its flattened form (a trans- verse section being oval), and by the partial volution of the apex; from Platyceras ( Orthonychia) striatum by its arcuate form, the prominent carina and the absence of conspicuous plications; from Pla
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