﻿THE 
  DESCENT 
  OF 
  SONNINIA 
  AND 
  HAMMATOCERAS. 
  651 
  

  

  •41. 
  The 
  Descent 
  of 
  Sonninia 
  and 
  Hammatoceras. 
  By 
  IS. 
  8. 
  

   Buckman, 
  F.G.S. 
  (Head 
  June 
  19, 
  1889.) 
  

  

  [Plate 
  XXII.] 
  

  

  Part 
  I. 
  — 
  Sonninia. 
  

  

  The 
  genus 
  Sonninia 
  was 
  founded 
  by 
  Bayle 
  * 
  to 
  take 
  the 
  place 
  of 
  

   his 
  Waagenia, 
  a 
  name 
  which 
  had 
  been 
  just 
  previously 
  used 
  ; 
  and 
  

   the 
  type 
  species 
  was 
  the 
  same, 
  Sonninia 
  (non 
  Waagenia) 
  propin- 
  

   quans 
  f, 
  Bayle. 
  

  

  The 
  species 
  which 
  are 
  closely 
  allied 
  to 
  Sonninia 
  propinquans 
  are 
  

   Sonninia 
  Sowerbyi 
  (Miller), 
  Sonn. 
  Broivni 
  (Sowerb} 
  r 
  ), 
  Sonn. 
  adicra 
  

   (Waagen), 
  Sonn. 
  mesacantha 
  (Waagen), 
  Sonn. 
  fissilobata 
  (Waag.), 
  

   and, 
  with 
  the 
  exception 
  of 
  the 
  last, 
  which 
  was 
  referred 
  to 
  Amaltheus 
  %, 
  

   these 
  species 
  were 
  located 
  by 
  Waagen 
  in 
  his 
  genus 
  Harpoceras. 
  In 
  

   this 
  he 
  was 
  followed 
  by 
  Wright 
  and 
  many 
  other 
  authors 
  ; 
  but 
  Neu- 
  

   mayr 
  § 
  relegated 
  them, 
  or 
  most 
  of 
  them, 
  to 
  Hyatt's 
  genus 
  Hamma- 
  

   toceras, 
  and 
  has 
  been 
  followed 
  herein 
  by 
  Zittel 
  |J 
  and 
  others. 
  Haug 
  % 
  

   makes 
  two 
  divisions 
  of 
  these 
  species 
  : 
  — 
  1st, 
  Gruppe 
  des 
  Ilamm. 
  

   Sowerbyi 
  ; 
  2nd, 
  Gruppe 
  des 
  Hamm. 
  Ogerieni 
  {Sonninia, 
  Bayle) 
  ; 
  

   and 
  his 
  opinion 
  is 
  that 
  the 
  Inferior-Oolite 
  species, 
  Amm. 
  propin- 
  

   quans, 
  Amm. 
  patella, 
  &c, 
  are 
  the 
  direct 
  descendants 
  of 
  the 
  Liassic 
  

   species, 
  Amm. 
  Ogerieni, 
  Amm. 
  navis, 
  &c. 
  

  

  Thus 
  far 
  the 
  history 
  of 
  the 
  species 
  embraced 
  by 
  the 
  genus 
  Son- 
  

   ninia. 
  My 
  present 
  object 
  is 
  to 
  show 
  their 
  probable 
  descent, 
  and 
  by 
  

   that 
  means 
  their 
  correct 
  relationship 
  in 
  a 
  genealogical 
  sense 
  to 
  

   various 
  genera. 
  

  

  The 
  supposition 
  that 
  Sonninia 
  propinquans 
  was 
  descended 
  from 
  

   Haugia 
  Ogerieni 
  takes 
  no 
  account 
  of 
  such 
  a 
  species 
  as 
  Sonninia 
  

   acanthodes, 
  n. 
  sp. 
  Whence 
  has 
  S. 
  acanthodes 
  derived 
  its 
  ventral 
  

   furrows 
  ? 
  and 
  how, 
  unless 
  we 
  suppose 
  a 
  case 
  of 
  atavism, 
  has 
  it 
  

   acquired 
  its 
  circular 
  (changing 
  to 
  quadrate) 
  evolute 
  whorls 
  ? 
  and, 
  

   instead 
  of 
  being 
  almost 
  smooth 
  as 
  we 
  should 
  expect 
  the 
  next 
  de- 
  

   scendant 
  of 
  Haugia 
  Ogerieni 
  to 
  be, 
  how 
  has 
  it 
  acquired 
  its 
  large 
  

   spines 
  and 
  coarse 
  ribs 
  ? 
  At 
  the 
  same 
  time 
  its 
  suture-line 
  is 
  more 
  

   highly 
  ornamented 
  than 
  that 
  of 
  Haugia 
  Ogerieni, 
  which, 
  had 
  it 
  been 
  

   a 
  case 
  of 
  atavism, 
  would, 
  I 
  fancy, 
  hardly 
  be 
  the 
  case. 
  It 
  may, 
  

   however, 
  be 
  urged 
  that 
  if 
  the 
  quadrate-whorled 
  evolute 
  S. 
  acan- 
  

  

  * 
  Bull. 
  Soc. 
  Geol. 
  France, 
  ser. 
  3, 
  vol. 
  vii. 
  p. 
  92 
  (1878-79). 
  

  

  t 
  Explic. 
  Carte 
  geol. 
  France 
  ; 
  Explan. 
  of 
  plate 
  lxxxiv. 
  

  

  | 
  " 
  Die 
  Formenreihe 
  Amm. 
  stibradiatus," 
  Greogn. 
  Pal. 
  Beitrage, 
  Bd. 
  ii. 
  Heft 
  

   ii. 
  p. 
  248, 
  footnote. 
  

  

  § 
  " 
  Ueber 
  unverrnittelt 
  auftretende 
  Cephalopotlen-typen," 
  Jahrbuch 
  k. 
  k. 
  

   geol. 
  Beichsanstalt, 
  Bd. 
  xxviii. 
  1878. 
  

  

  || 
  Handbuch 
  der 
  Palaontologie, 
  " 
  Cephalopoden," 
  p. 
  461. 
  

  

  5T 
  " 
  Beitr. 
  Monogr. 
  Harp.," 
  Neues 
  Jahrbuch 
  fur 
  Mineral. 
  &c, 
  Beil.-Bd. 
  iii. 
  

   p. 
  654 
  et 
  seq. 
  

  

  