. Bulletin of the Buffalo Society of Natural Sciences. Natural history; 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. Brachidinm consisting of two spiral cones arranged base to base, connected by a V-shaped jugum. Whitiieldella nitida Hall (Fig. 123). Atrypa n i t i d
. Bulletin of the Buffalo Society of Natural Sciences. Natural history; 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. Brachidinm consisting of two spiral cones arranged base to base, connected by a V-shaped jugum. Whitiieldella nitida Hall (Fig. 123). Atrypa n i t i d a 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 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. Found abundantly in the Clinton 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. Fig. 123 Whitfieldella nitida Whitiieldella nitida var. oblata Hall (Fig. 124). Atrypa nitida var. oblata Hall (1852. Pal. N. Y. 2:269, pi. 55) Distinguishing characters. Broadly ovate form, angle between cardinal slopes often 900 or more; moder- ately convex valves, subtriangular in cross-section; uniformly rounded front; surface absolutely smooth, very deep muscular impressions. Found in the Clinton lenses and the Rochester shale associated with the preceding and usually more abundant. Also at Lockport, etc. (Flail).. Fig. 124 Whitfieldella nitida var. oblata. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly r
Size: 1325px × 1886px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, books, booksubjectnaturalhistory
