. Bulletin - New York State Museum. Science. NIAGARA FALLS AND VICINITY 183 subauriculate; cardinal areas narrow, sometimes obscurely crenu- lated on the margins. Delthyrium partially closed by convex plate, but mostly occupied by cardinal process of opposite valve. Car- dinal process appears trilobate. Muscular areas moderately well defined. Plectambonites sericea (Sowerby) (Fig. 89). Leptaena sericea Hall (1852. Pal. N. Y. 2:59, pi. 21) Distinguishing characters. Outline semicircular to semioval; hinge line ex- tended, ending in acute points; striae strong, elevate
. Bulletin - New York State Museum. Science. NIAGARA FALLS AND VICINITY 183 subauriculate; cardinal areas narrow, sometimes obscurely crenu- lated on the margins. Delthyrium partially closed by convex plate, but mostly occupied by cardinal process of opposite valve. Car- dinal process appears trilobate. Muscular areas moderately well defined. Plectambonites sericea (Sowerby) (Fig. 89). Leptaena sericea Hall (1852. Pal. N. Y. 2:59, pi. 21) Distinguishing characters. Outline semicircular to semioval; hinge line ex- tended, ending in acute points; striae strong, elevated, alternating with finer ones. Found in the lower Clinton limestone at Niagara. Rare. Plectambonites transversalis (Wahlenberg) (Fig. 90). Lep- taena transversalis Hall (1852. Pal. N. Y. ^6, pi. 53. fig- 5a-b) Distinguishing characters. Out- .^^^^^^ line semicircular; strongly convex ^^HH^v pedicle, and extremely concave bra- ^^K/^ '4«,is.^ chial valve, conforming to each other; strongly incurved beak of pedicle valve, which causes an inflection of the hinge line; hinge line produced; Fig. 90 Plectambonites transversalis ^ ,, , , . , line distant elevated striae with ex- tremely fine striae between; strongly punctate character of ex- foliated portions. Found in the Clinton lenses, and abundantly in the lower Roches- ter shale at Niagara. Also at Lockport (Hall). Genus orthothetes Fischer de Waldheim [Ety.: opdo?^ straight] (1830. Soc. imp. natural, d. Moscow Bui. 1:375. Hall & Clarke, 1892; Pal. N. Y. V. 8, pt I, p. 253) Shell varying from plano-convex to biconvex, sometimes becom- ing concavo-convex with age. Pedicle valve most convex about the beak, which often tends toward irregular growth; cardinal area well developed, with a thick, more or less convex deltidium. Teeth not supported by dental plates. Brachial valve mast convex near. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - colorati
Size: 2055px × 1216px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectscience, bookyear1887
