. The Geology of Minnesota . ior of a left valve, showing the hinge with its cardinal teeth, escutcheon and posterior internal ligament supports, and faint muscular outline is imperfect posteriorly, causing the shell to appear less obliquethan it should be. Hudson River group. Spring Valley, Minnesota. Figs. 33 and 34. Technophorus subacutus Ulrich 614 Cast of the interior of the natural size and twice magnified. Trenton limestone,Minneapolis, Minnesota. Geol. Sur. Mus. Reg. No. 8338. Figs. .35 and ,36. TBCiiNorHOuus filistriatus Ulrich 615 Left valve of the natural size and a
. The Geology of Minnesota . ior of a left valve, showing the hinge with its cardinal teeth, escutcheon and posterior internal ligament supports, and faint muscular outline is imperfect posteriorly, causing the shell to appear less obliquethan it should be. Hudson River group. Spring Valley, Minnesota. Figs. 33 and 34. Technophorus subacutus Ulrich 614 Cast of the interior of the natural size and twice magnified. Trenton limestone,Minneapolis, Minnesota. Geol. Sur. Mus. Reg. No. 8338. Figs. .35 and ,36. TBCiiNorHOuus filistriatus Ulrich 615 Left valve of the natural size and a small portion of the surface enlarged toshow the regular character of the fine concentric lines. Upper part of themiddle third of the Trenton shales, Goodhue county, Minnesota. Figs. 37 and 38. TECnNOPHORUS divakicatus Ulrich 616 The type specimen, a perfect left valve, of the natural size and enlarged two andone-half times. UpperthirdoftheTrenton shales, near Cannon Falls,Minnesota. y^^ 111^ 1 LamellilDrancluata j Plate Figs. 10 to 14. 10 to 12. 13 and 14. Figs. 15 and 16. Figs. 17 to 21 17. 18. 19 and 20. PLATE XLI. Page. Fig. 1. WniTELLA iiUGATiNA, n. sp 569 Left side of a cast of the interior. Middle third of the Trenton shales, Minne-apolis, Minnesota. Figs. 2 and 3. Whitella concenteica Ulrich 569 The right side and a front view of the type. Middle third of the Trenton shales,Minneapolis, Minnesota. Figs. 4 and 5. Whitella megasiisona Whitfield, sp 570 Two views, lateral and anterior, of a good cast of the interior. Trenton lime-stone, Minneapolis, Minnesota. Figs. 6 to 9. Whitella COJIPRESSA Ulrich 568 6 and 7. The right side and a front view of an internal cast, differing slightly from the type of the and 9. Two views, side and dorsal, of the original type of the species. Middle third of the Trenton shales, Minneapolis, Minnesota. Whitella truncata Ulrich 572 Dorsal, side and front views of an average specimen. The right side and a posterior view of the l
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