. Annual report of the Regents. New York State Museum; Science. NIAGARA FALLS AND VICINITY 195 Rhynchonella (?) bidentata (HisingerJ (Fig. iii). Atrypa bidentat-a Hall (1852. Pal. N. Y. 2:276, pl. 57) Distinguishing characters. Triangular form; acute, extended beak of pedicle valve; stronger convexity o-f brachial valve; less convex and more triangularly acute than preceding; very slight . ^ , . ^. , „ . , ,. Fig. m Rhynchcnel- frontal emarefination; shallow smus with one ph-ia (?) wdentata with *^ surface enlarged cation, and corresponding fold with two. Found in the Rochester shale at Lockpo
. Annual report of the Regents. New York State Museum; Science. NIAGARA FALLS AND VICINITY 195 Rhynchonella (?) bidentata (HisingerJ (Fig. iii). Atrypa bidentat-a Hall (1852. Pal. N. Y. 2:276, pl. 57) Distinguishing characters. Triangular form; acute, extended beak of pedicle valve; stronger convexity o-f brachial valve; less convex and more triangularly acute than preceding; very slight . ^ , . ^. , „ . , ,. Fig. m Rhynchcnel- frontal emarefination; shallow smus with one ph-ia (?) wdentata with *^ surface enlarged cation, and corresponding fold with two. Found in the Rochester shale at Lockport and elsewhere (Hall). Probably also at Niagara. Genus atrypa Dalman [Ety.: a, without; rpu-a, foramen (erroneous)] (1828. Kongl. Vetenskaps Akad. Handlingar, p. 127; 1894. Pal. N. Y. V. 8, pt 2, p. 163) Shell varying in outline from nearly circular to longitudinally suboval; valves very unequal, brachial valve being strongly convex or gibbous, while the pedicle valve is gently convex or almost flat or sometimes slightly concave from the strongly marked sinus; beak of the pedicle valve small and incurved over that of the brachial. Large widely separated and doubly grooved teeth are present, unsupported by lamellae. Strong muscular impressions. Spirals of the brachidium with their bases parallel to the inner sur- face of the pedicle valve, and the apexes directed toward the deepest point of the opposite valve. Surface radially plicate. Atrypa reticularis (Linnaeus) (Fig. 112) (1852. Pal. N. Y. 2:272, pl. 23, p. 270, pl. 55). Fig. 112 Atrypa reticularis Distinguishing characters. Convex brachial and flat pedicle valves; small deeply incurved beaks; radiating and concentric striae forming reticulated 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; University of the State of
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