. The microscope and its revelations. FIG. 702. FIG. 703. FIG. 704. FIG. 702.—Horizontal section of shell of Terebratula buJlata (fossil, 703. „ „ Megerlia lima (fossil, Chalk). FIG. 704. „ „ Spiriferina rostrata (Triassic). fossil Brachiopods, these canals are almost entirely absent : sothat the uniformity of their presence in the Terebratulidce, and theirgeneral absence in the Rhynchonettidce, supply a character ofgreat value in the discrimination of the fossil , belongingto these two groups respectively. Great caution is , in applying this test; mere surf
. The microscope and its revelations. FIG. 702. FIG. 703. FIG. 704. FIG. 702.—Horizontal section of shell of Terebratula buJlata (fossil, 703. „ „ Megerlia lima (fossil, Chalk). FIG. 704. „ „ Spiriferina rostrata (Triassic). fossil Brachiopods, these canals are almost entirely absent : sothat the uniformity of their presence in the Terebratulidce, and theirgeneral absence in the Rhynchonettidce, supply a character ofgreat value in the discrimination of the fossil , belongingto these two groups respectively. Great caution is , in applying this test; mere surfaa nt«rl.•/////* r,//t,//>t berelied on ; and no statement on this point is worthy of reliancewhich is not based on a microscopic examination of thin sections ofthe shell. In the families Spiriferidce and Strophomenidce, 011 theother hand, some species possess the perforations, whilst others aredestitute of them ; so that their presence or absence t/ierc serves onlyto mark out subordinate groups. This, however, is wha
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
