orthocerasn.

1734 Philos. Trans. 1733–4 (Royal Soc.) 38 192 The sixth Chapter is of the Orthoceras and Orthoceratites, or stony Concretion in its Cavity. Of these last Stones he produces nine different Species, which he distinguishes chiefly by the Pipe, or Canal, which runs through them.

1830 C. Lyell Princ. Geol. I. 101 The gigantic orthocerata of this era being, to recent multilocular shells, what the fossil ferns, equiseta, and other plants of the coal strata, are in comparison with plants now growing within the tropics.

1863 C. Lyell Geol. Evid. Antiq. Man xx. 404 It is said truly that the ammonite, orthoceras, and nautilus of these ancient rocks were of the tetrabranchiate division.

1873 Jrnl. Amer. Geogr. Soc. N.Y. 1872 3 240 Shales..containing Ichthyodorulites and other fossils, among which may be mentioned an Orthoceras.

1901 Science 24 May 825/2 He had collected 18 varieties of goniatites, orthocerata, and related forms, nearly all of them confined to the upper layer of limestone.

1928 Science 27 July 85 An orthoceras, plus many gastropods and pelecypods have been found.

1970 R. M. Black Elements Palaeontol. viii. 78 Orthoceras and similar orthocones range in length from about 3 cm to possibly 460 cm.

1992 Rock & Gem Feb. 5/2 (advt.) Orthoceras fossils: Range in size from 4–8′.

1884 Science 1 Feb. 127/1 Evidence..that the Ammonoidea, with their distinct embryos, arose from the orthoceran stock.

1901 Amer. Naturalist 35 39 Until a few years ago Baculites was supposed to be an ammonite that had reverted to the orthoceran form.

1944 Amer. Midland Naturalist 32 766 The structural pattern which Dunbar..figured for Atractites, namely a simple and well defined orthoceran living chamber orad of the phragmocone.