﻿234 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  Stephanoceras 
  Blagdeni. 
  

  

  Braikenridgii. 
  

  

  Brocchii. 
  

  

  coronatum. 
  

  

  Brongniarti. 
  

  

  Stephanoceras 
  Deslongchampsii. 
  

  

  G-ervillii. 
  

  

  Humphriesianum. 
  

  

  Sauzei. 
  

  

  Banksii. 
  

  

  The 
  globose 
  form 
  of 
  Stephanoceras 
  macrocepJialum 
  represents 
  a 
  

   distinct 
  group, 
  characterized 
  by 
  the 
  smallness 
  of 
  the 
  umbilicus, 
  ex- 
  

   treme 
  involution 
  of 
  the 
  shell, 
  and 
  long 
  siphonal 
  lobe. 
  Steph. 
  

   modiolare 
  possesses 
  the 
  same 
  lobal 
  conditions. 
  This 
  group 
  of 
  the 
  

   Stephanocerata 
  is 
  not 
  specifically 
  rich 
  in 
  the 
  European 
  rocks, 
  and 
  

   occupies 
  a 
  limited 
  horizon 
  in 
  time. 
  In 
  England 
  and 
  Germany 
  the 
  

   above 
  group 
  commences 
  in 
  the 
  Cornbrash, 
  and 
  occurs 
  in 
  the 
  Kella- 
  

   ways 
  Rock 
  and 
  Oxford 
  Clay. 
  Dr. 
  Waagen, 
  in 
  the 
  " 
  Jurassic 
  Cepha- 
  

   lopoda 
  " 
  (Palseontologia 
  Indica), 
  has 
  figured 
  and 
  described 
  23 
  species 
  

   of 
  Stephanoceras 
  from 
  the 
  " 
  Kacch 
  Jura 
  ;" 
  of 
  these, 
  the 
  species 
  

   identical 
  with 
  European 
  forms 
  occupy 
  also 
  in 
  Kacch, 
  as 
  in 
  Europe, 
  

   the 
  true 
  " 
  Macrocephahis-beds." 
  The 
  group 
  of 
  the 
  Macrocephali 
  is 
  

   one 
  of 
  the 
  most 
  important 
  among 
  all 
  the 
  Jurassic 
  Ammonites, 
  for 
  

   nearly-allied 
  forms 
  have 
  been 
  found 
  over 
  the 
  whole 
  world. 
  

  

  Genus 
  Cosmoceras. 
  — 
  Von 
  Buch's 
  group 
  x. 
  (the 
  Ornati) 
  is 
  absorbed 
  

   by 
  Cosmoceras. 
  This 
  genus 
  first 
  appears 
  in 
  the 
  upper 
  beds 
  of 
  the 
  

   Inferior 
  Oolite, 
  where 
  the 
  species 
  Cosm. 
  Parkinsoni 
  and 
  Cosm. 
  

   Garantianum 
  abound 
  ; 
  they 
  arc 
  well 
  characterized 
  by 
  the 
  smooth 
  

   channel 
  in 
  the 
  middle 
  of 
  the 
  ventral 
  side, 
  which 
  interrupts 
  the 
  

   passing 
  of 
  the 
  ribs 
  across 
  the 
  siphonal 
  area. 
  In 
  the 
  Kellaways 
  and 
  

   Oxford 
  Clay 
  Cosmoceras 
  calloviense, 
  C. 
  Duncani, 
  C. 
  Koenigi, 
  C. 
  

   Gowerianum, 
  and 
  C. 
  jason 
  abound. 
  The 
  highly 
  ornamented 
  shells 
  

   and 
  other 
  constant 
  characters 
  well 
  deserved 
  the 
  name 
  applied 
  to 
  the 
  

   group 
  by 
  Yon 
  Buch. 
  The 
  genus 
  ranges 
  into 
  the 
  Chalk 
  under 
  the 
  

   form 
  of 
  Cosm. 
  verrucosum, 
  D'Orb. 
  

  

  Genus 
  Ancyloceras, 
  D'Orb. 
  — 
  Spirally 
  rolled 
  on 
  the 
  same 
  plane, 
  

   the 
  " 
  whorls 
  all 
  disjointed 
  and 
  separate," 
  the 
  last 
  projected 
  in 
  a 
  

   horizontal 
  direction, 
  then 
  turning 
  upwards 
  and 
  inwards, 
  opposed 
  or 
  

   opposite 
  to 
  the 
  spiral 
  coil 
  ; 
  the 
  septa 
  are 
  transverse, 
  symmetrical, 
  

   and 
  6-lobed, 
  unequal 
  in 
  size, 
  and 
  composed 
  of 
  ramified 
  elongated 
  

   digitations. 
  The 
  earliest 
  form 
  known 
  is 
  Ancyloceras 
  annulatum, 
  

   from 
  the 
  Lower 
  Jurassic 
  beds 
  of 
  England 
  and 
  France 
  ; 
  with 
  it, 
  in 
  

   the 
  Inferior 
  Oolite 
  of 
  Germany, 
  occurs 
  Ancyl. 
  baculatum. 
  The 
  

   Kellaways 
  Kock 
  yields 
  one, 
  Ancyl. 
  calloviense. 
  Ancyloceras 
  attains 
  

   its 
  greatest 
  development 
  in 
  the 
  Lower 
  Cretaceous 
  rocks 
  (Neocomian), 
  

   the 
  two 
  chief 
  forms 
  being 
  Ancyl. 
  Matheronianum 
  and 
  Ancyl. 
  Puzo- 
  

   sianum. 
  Ancyl. 
  gigas, 
  Hillsii, 
  grande, 
  and 
  Matheronianum 
  are 
  

   British 
  Cretaceous 
  species. 
  

  

  Genus 
  Perisphinctes, 
  Waagen. 
  — 
  The 
  singular 
  Ammonite 
  P. 
  Mar- 
  

   tinsii, 
  D'Orb., 
  from 
  the 
  Inferior 
  Oolite 
  of 
  England 
  and 
  Prance, 
  is 
  

   the 
  only 
  example 
  we 
  have. 
  Dr. 
  Waagen 
  enumerates 
  nearly 
  60 
  

   species 
  from 
  the 
  Kacch 
  Jura 
  (Cutch). 
  "These 
  can 
  be 
  distributed 
  

   into 
  6 
  large 
  sections, 
  comprising 
  several 
  groups 
  that 
  find 
  their 
  equi- 
  

   valents 
  in 
  the 
  Middle 
  and 
  Upper 
  Jurassic 
  rocks 
  of 
  Europe, 
  between 
  

  

  