. Bulletin - New York State Museum. Science. i84 NEW YORK STATE MUSEUM the middle, with a narrow hinge area; cardinal process quadrilobate as seen from above. Surface covered by slender radiating striae^ which are crenulated by concentric lines. Orthothetes subplanus (Conrad) (Fig. 91). Leptaena sub- plana Hall (1852. Fa/. A^. F. 2:259, pi. 53, fig. 8-10) Distinguishing characters. Pedicle valve at first convex, later be- coming concave; valves nearly equal in length and width; extended hinge line, sometimes projecting into points; sharp angular or sub- angular to rounded striae, sometimes bif
. Bulletin - New York State Museum. Science. i84 NEW YORK STATE MUSEUM the middle, with a narrow hinge area; cardinal process quadrilobate as seen from above. Surface covered by slender radiating striae^ which are crenulated by concentric lines. Orthothetes subplanus (Conrad) (Fig. 91). Leptaena sub- plana Hall (1852. Fa/. A^. F. 2:259, pi. 53, fig. 8-10) Distinguishing characters. Pedicle valve at first convex, later be- coming concave; valves nearly equal in length and width; extended hinge line, sometimes projecting into points; sharp angular or sub- angular to rounded striae, sometimes bifurcating before reaching. Fig. 91 Orthothetes subplanus margin, separated by wider interspaces; the usual method of increase is by intercalation of fine striae, which soon grow to strength of the chief ones; fine concentric and occasionally coarser lines of growth. Found at Niagara in the upper Clinton beds and the Clinton lenses; also abundantly in certain thin calcareous layers of the lower Rochester shale, less common in the middle and upper shale. Also at Lockport and elsewhere (Hall). Orthothetes hydraulicus (Whit- field) (Fig. 92) (Grabau. GeoL soc. Am, Bui. II :365, pi. 22) Distinguishing char actors. Small size; obtuse cardinal margins with hinge line shorter than greatest width of shell; uniformly rounded front; strong rounded, sharply de-. 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 resemble the original New York State Museum; New York State Museum. Albany : New York State Education Dept
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectscience, bookyear1887
