. Bulletin - New York State Museum. Science. 202 NEW YORK STATE MUSEUM curved, usually exposing the circular apical foramen, beneath which the deltidial plates are frequently retained. Cardinal slopes of both valves broad and not distinctly defined; anterior margin subtruncate and gently sinuate. Hinge plate in brachial valve concave, divided by a deep central concavity, which is supported by a medium septum. Brachidium consisting of two spiral cones arranged base to base, connected by a V-shaped jugum. Whitfieldella nitida Hall (Fig. 123). Atrypa nitida Hall (1852. Pal. N. Y. 2:268, pi. 55) D
. Bulletin - New York State Museum. Science. 202 NEW YORK STATE MUSEUM curved, usually exposing the circular apical foramen, beneath which the deltidial plates are frequently retained. Cardinal slopes of both valves broad and not distinctly defined; anterior margin subtruncate and gently sinuate. Hinge plate in brachial valve concave, divided by a deep central concavity, which is supported by a medium septum. Brachidium consisting of two spiral cones arranged base to base, connected by a V-shaped jugum. Whitfieldella nitida Hall (Fig. 123). Atrypa nitida Hall (1852. Pal. N. Y. 2:268, pi. 55) Distinguishing characters. Small size; strong convexity of valves, which are nearly equal, pointed incurved beak of V •::' ^ pedicle valve; smooth surface except for concentric growth lines and strong wrinkles of growth; often slight sinus near the front of both valves, causing slight frontal emargination. Fig. 123 Whitfieldella nitida -^^ , , . '.,„,. , hound abundantly m the Clmton lenses and less commonly in the Rochester shale at Niagara. This species varies from broadly to narrowly ovate; the thick- ness is frequently greater than the width and coarse thickenings and wrinkles show changes in growth. This may characterize senile individuals. Whitfieldella nitida var. oblata Hall (Fig. 124). Atrypa nitida var. oblata Hall (1852. Pa/. TV. F. 2:269, pi. 55) Distinguishing characters. Broadly ovate form, angle between cardinal slopes often 90° or more; moder- aH^'- ^ ately convex valves, subtriangular in ^^/ \W' cross-section; uniformly rounded front; surface absolutely smooth, verv ^. ,0. wr,;- ,^ n -^-^ ' J ' ^' Fig. 124 Whitfieldella nitida var. oblata deep muscular impressions. Found in the Clinton lenses and the Rochester shale associated with the preceding and usually more abundant. Also at Lockport, etc. (Hall).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectscience, bookyear1887
