. The Devonian of Missouri. Geology; Geology, Stratigraphic; Paleontologie; Devoon. CEPHALOPODA. 159 ured on the inside curvature. Transverse section of the shell obtusely subtriangular, flattened or but slightly convex on the inner surface, rounded on the lateral surfaces, and obtusely rounded on the back; the dorso-ventral and lateral diameters are about as four and five, and the triangular form is more perceptible in the earlier stages of growth, owing to the greater convexity of the inner face in the upper portion and on the outer chamber. Outer chamber comparatively short, being about two
. The Devonian of Missouri. Geology; Geology, Stratigraphic; Paleontologie; Devoon. CEPHALOPODA. 159 ured on the inside curvature. Transverse section of the shell obtusely subtriangular, flattened or but slightly convex on the inner surface, rounded on the lateral surfaces, and obtusely rounded on the back; the dorso-ventral and lateral diameters are about as four and five, and the triangular form is more perceptible in the earlier stages of growth, owing to the greater convexity of the inner face in the upper portion and on the outer chamber. Outer chamber comparatively short, being about two-thirds as high as wide. Aperture large, irregularly tri-lobed, straight on the inner face and about four-fifths as wide as the entire width of the shell, and apparently about two-thirds as wide in a dorso-ventral direction as laterally. The exact form of the aperture on the outer side cannot be ascertained, owing to the imperfection of the specimen in this part. Septa moderately concave, very closely arranged in the lower part but more distinctly dis- posed above; the rate of increase in distance somewhat gradual to near the upper portion, where two or three'of the septa are slightly more crowded. In the more distant portions three chambers occupy the space of one inch, but in the lower part of the specimen, where the transverse d'ameter is a little more than one and a half inches, they are less than one-twelfth of an inch apart. Siphuncle of moderate size and subcentrally situated. Surface of the shell ; Remarks—A specimen from the Grand Tower limestone probably belongs to this species though the lack of diagnostic characters of the group makes positive identifica- tion impossible in most cases. The specimen is larger than the one figured by Whitfield and it does not show as much curvature as that specimen. More of the smaller end is missing than in the Ohio specimen. The aperture, shape, size, and living chamber are much alike in the specimens from Ohio and Mi
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectgeology, bookyear1922
