. Bulletins of American paleontology. 82 Bulletin 150 228 kind possessing flanges found in pre-Devonian rocks. Unfortunately, since only one specimen was available for study, it has not been pos- sible to elucidate the structure of the siphuncle. Judging from gen- eral shell morphology the genus can be supposed to belong either to the Tarphyceratidae or the Plectoceratidae. Since the former family is much more abundantly represented in Upper Canadian rocks than the latter, we believe that Aethoceras may eventually be found to belong to the Tarphyceratidae. Aethoceras caurns Teichert and Glenis
. Bulletins of American paleontology. 82 Bulletin 150 228 kind possessing flanges found in pre-Devonian rocks. Unfortunately, since only one specimen was available for study, it has not been pos- sible to elucidate the structure of the siphuncle. Judging from gen- eral shell morphology the genus can be supposed to belong either to the Tarphyceratidae or the Plectoceratidae. Since the former family is much more abundantly represented in Upper Canadian rocks than the latter, we believe that Aethoceras may eventually be found to belong to the Tarphyceratidae. Aethoceras caurns Teichert and Glenister, PI. 9, figs. 8-10; text fig. 15 Description of holotype (No. 364, Bureau of Mineral Resources, Geology and Geophysics, Canberra).—The holotype is an internal mould of a shell which consists of slightly more than one whorl of a loosely coiled torticone with a maximum diameter of 23 mm. The whorls are almost in contact, but a depressed zone is not developed. One quarter of the last whorl is represented by body chamber. The lateral diameter of the body chamber at its adapertural end is 10 mm., its dorso-ventral diameter 7 to 8 mm. The shell has been re- moved from one side of the specimen but remains intact on the op- posite side. A consideration of the rate of expansion of the whorls indicates that the shell was widely perforate. At the beginning of the last preserved whorl the mid-ventral axis of that whorl lies about 4 mm. off the plane of symmetry of the body chamber at its apertural end, thus affording a measure of the helicoidal coiling of the Fig. 15. Cross-section of Aethoceras caurus, X 5. The whorls are slightly depressed and evenly rounded across the dorsum and venter. Where the lateral diameter is mm, and the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Paleontological R
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