MEMOIR 13 Nautiloid Shell Morphology By ROUSSEAU H. FLOWER STATEBUREAUOFMINESANDMINERALRESOURCES NEWMEXICOINSTITUTEOFMININGANDTECHNOLOGY CAMPUSSTATION SOCORRO, NEWMEXICO MEMOIR 13 Nautiloid Shell Morphology By ROUSSEAU H. FLOIVER 1964 STATEBUREAUOFMINESANDMINERALRESOURCES NEWMEXICOINSTITUTEOFMININGANDTECHNOLOGY CAMPUSSTATION SOCORRO, NEWMEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Alvin J. Thompson, Director THE REGENTS MEMBERS EXOFFICIO THEHONORABLEJACKM.CAMPBELL ................................ Governor of New Mexico LEONARDDELAY() ................................................... Superintendent of Public Instruction APPOINTEDMEMBERS WILLIAM G. ABBOTT ................................ ................................ ............................... Hobbs EUGENE L. COULSON, M.D ................................................................. Socorro THOMASM.CRAMER ................................ ................................ ................... Carlsbad EVA M. LARRAZOLO (Mrs. Paul F.) ................................................. Albuquerque RICHARDM.ZIMMERLY ................................ ................................ ....... Socorro Published February 1 o, 1964 For Sale by the New Mexico Bureau of Mines & Mineral Resources Campus Station, Socorro, N. Mex.—Price $2.50 Contents Page ABSTRACT ....................................................................................................................................................... 1 INTRODUCTION ............................................................................................................ I General purpose ....................................................................................................................................... I History ........................................................................................................................................................ 3 Terminology ........................................................................................................................ 4 General shell organization ...............................................................................................................................4 A note on shell habit ................................................................................................................................ 5 CONCH ........................................................................................................................................................... 7 General features .........................................................................................................................................7 Shell form ...................................................................................................................................................7 Composition ...............................................................................................................................................9 Apertures ................................................................................................................................................. 10 Ornament ................................................................................................................................................. 10 Conch interior ........................................................................................................................................ 11 Protoconch ............................................................................................................................................... 12 SEPTA ............................................................................................................................................................... 14 General structure ....................................................................................................................... 14 Composition ............................................................................................................................................. 14 Regions of the septum ............................................................................................................................ 15 CONNECTING RING ......................................................................................................... 18 General structure ................................................................................................................ 18 Plectronoceratina ....................................................................................................................... 18 Ellesmeroceratina .............................................................................................................................. 20 Cyrtoceratina .................................................................................................................................... 21 Actinoceratida ......................................................................................................................................... 21 Endoceratida ............................................................................................................................................. 22 Tarphyceratida ........................................................................................................................ 23 The discosorid ring .................................................................................................................................. 23 Oncoceratida ............................................................................................................................................ 23 Thin, apparently homogeneous, rings ............................................................................................ 26 THE SIPHON OR SIPHUNCLE .............................................................................................. 27 SIPHONAL DEPOSITS ............................................................................................................. 29 General relationships ............................................................................................................ 29 Ellesmeroceratida ............................................................................................................................. 29 Discosorida, the fibralia .......................................................................................................................... 31 The endoceroid endosiphuncle ............................................................................................................. 32 Actinoceratida .......................................................................................................................................... 37 Michelinoceratida ............................................................................................................................. 38 Other orders ............................................................................................................................... 41 CAMERAL DEPOSITS .............................................................................................................. 42 ORIENTATION ........................................................................................................................................... 46 GLOSSARY .................................................................................................................................................... 48 Page SUPPLEMENTARY NOTES ...................................................................................................... 54 Protocycloceras affine ........................................................................................................... 54 Diaphragms in the Endoceratida .......................................................................................................... 55 Dideroceras .............................................................................................................................................. 55 Dideroceras wahlenbergi ................................................................................................. 55 Dideroceras magnum .................................................................................................. 56 Dideroceras gracile ............................................................................................................... 56 Dideroceras holmi ..................................................................................................... 56 Dideroceras ventrale ............................................................................................................. 56 Bisonoceras .............................................................................................................................................. 56 Bisonoceras corniforme ............................................................................................................... 57 Bisonoceras spp. ............................................................................................................................... 58 Disphenoceras ......................................................................................................................................... 58 Disphenoceras conicum .............................................................................................. 58 Dartonoceras ...........................................................................................................................................