. Annual report of the regents of the university of the state of New York on the condition of the State Cabinet of Natural History and the historical and antiquarian collection annexed thereto. Science. 358 TWENTIETH REPORT ON THE STATE CABINET. CYRTOCERAS RIGIDUM. PLATE 16 (7), FIGS. 3-5. Shell small, consisting of about one volution, gradually expanding to a diameter of three-fourths of an inch with a height of two inches. Septa unknown; outer chamber deep. Siphuncle apparently dorsal. Surface of cast marked by strong obliquely transverse annulations which become gradually stronger from the
. Annual report of the regents of the university of the state of New York on the condition of the State Cabinet of Natural History and the historical and antiquarian collection annexed thereto. Science. 358 TWENTIETH REPORT ON THE STATE CABINET. CYRTOCERAS RIGIDUM. PLATE 16 (7), FIGS. 3-5. Shell small, consisting of about one volution, gradually expanding to a diameter of three-fourths of an inch with a height of two inches. Septa unknown; outer chamber deep. Siphuncle apparently dorsal. Surface of cast marked by strong obliquely transverse annulations which become gradually stronger from the concave side, and are gently curved back- ward on the middle of the dorsum. Spaces between the annulations concave, without any evidence of intermediate smaller ridges. Exterior surface unknown, the specimen being a cast of the interior. The figures referred to are the dorsal and lateral views of a fragment, with a transverse section. The accompanying outline figure shows the form of the entire cast of the interior, as nearly as can be given with materials in my Formation and locality. In limestone of the age of the Niagara group, at Bridgeport, Illinois. CYRTOCERAS (Phragmoceras?) AMPLICORNE (n. s.). =tt|>h> 6- PLATE 17 (8), FIGS. 6 & 7. (Figures one-third less than natural size). Shell large, strongly curved, making an entire volution, rapidly expand- ing toward the outer chamber, which is less arcuate than the septate portions of the shell; transverse section broadly elliptical, becoming a little flattened on the sides towards the outer chamber. Septa rather deeply concave and comparatively distant; three of them, measured on the dorsum, being nearly equal to the diameter of the outer part of the largest one measured. The dorsal margins of the septa are advanced so that a direct transverse section would cut the ventral margin of the next preceding one. Siphuncle small, central or subcentral. Entire form of aperture unknown. Surface finely striated, wit
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectscience, bookyear1853
