﻿10 
  PROCEEDINGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOClEXr. 
  

  

  The 
  rhachidian, 
  as 
  a 
  whole, 
  conveys 
  an 
  impression 
  of 
  extreme 
  

   sharpness 
  in 
  all 
  its 
  cusps 
  and 
  denticles. 
  The 
  absence 
  of 
  the 
  buttress 
  

   in 
  the 
  two 
  side 
  cusps, 
  and 
  the 
  less 
  powerful 
  pillar 
  on 
  which 
  the 
  

   central 
  cusp 
  rests, 
  appear 
  decisively 
  to 
  range 
  the 
  species 
  with 
  the 
  

   southern 
  and 
  not 
  with 
  the 
  northern 
  group. 
  

  

  In 
  all 
  the 
  species 
  under 
  consideration, 
  except 
  miiricata, 
  the 
  laterals 
  

   afford 
  little 
  assistance 
  in 
  grouping, 
  for 
  («) 
  their 
  shape 
  is, 
  in 
  

   essentials, 
  similar 
  throughout, 
  (i) 
  experience 
  shows 
  that 
  a 
  very 
  slight 
  

   change 
  in 
  the 
  position 
  of 
  a 
  lateral 
  on 
  the 
  slide 
  often 
  appears 
  to 
  

   indicate 
  a 
  change 
  of 
  shape 
  wliich 
  is 
  not 
  really 
  existent. 
  Special 
  

   care 
  is 
  needed 
  in 
  basing 
  conclusions 
  upon 
  the 
  laterals 
  in 
  this 
  and 
  the 
  

   allied 
  groups 
  {Thais, 
  Morula, 
  etc.). 
  

  

  The 
  whole 
  group 
  will 
  work 
  out 
  as 
  follows: 
  — 
  

  

  Subgenus 
  Acanthina, 
  G. 
  Fischer, 
  1807, 
  Mus. 
  Demidoff, 
  iii, 
  p. 
  174 
  

   (= 
  Monoceros, 
  Lam. 
  (pars), 
  1822, 
  Anim. 
  s. 
  vert., 
  vii, 
  p. 
  250). 
  

  

  1. 
  Acanthina 
  calcar 
  (Martyn). 
  

   1784. 
  Buccimim 
  calcar, 
  Martyn, 
  Universal 
  Conchologist, 
  i, 
  f. 
  10. 
  

   1786. 
  B. 
  monodon, 
  Solander, 
  Portland 
  Cat., 
  p. 
  17, 
  No. 
  372. 
  

  

  1788. 
  B. 
  monodon, 
  Grnelin 
  : 
  Linne, 
  Syst. 
  Nat., 
  13th 
  ed., 
  p. 
  3483, 
  

  

  No. 
  50. 
  

   1788 
  (?). 
  B. 
  calcar 
  -long 
  urn, 
  Martyn, 
  TJniv. 
  Conch., 
  ii, 
  f. 
  50. 
  

   1822. 
  Monoceros 
  imhricatmn, 
  Lamarck, 
  Anim. 
  s. 
  vert., 
  vii, 
  p. 
  251. 
  

   1822. 
  3/. 
  striatum, 
  Lamarck, 
  Anim. 
  s. 
  vert., 
  vii, 
  p. 
  251. 
  

   1822. 
  M. 
  breve, 
  Sowerby, 
  Genera 
  No. 
  5, 
  pi. 
  ccxxxix, 
  f. 
  2. 
  

   1835. 
  M. 
  acuminatum, 
  Sowerby, 
  Proc. 
  Zool. 
  Soc. 
  Lond., 
  p. 
  50. 
  

   Var. 
  unicornis, 
  Brug. 
  

  

  1789. 
  Buccinum 
  unicorne, 
  Bruguiere, 
  Encycl. 
  Meth., 
  Vers, 
  i, 
  p. 
  254. 
  

   1822. 
  Monoceros 
  crassilahrum, 
  Lamarck, 
  Anim. 
  s. 
  vert., 
  vii, 
  p. 
  252. 
  

   1822. 
  M. 
  glahratmn, 
  Lamarck, 
  Anim. 
  s. 
  vert., 
  vii, 
  p. 
  251. 
  

  

  1835. 
  M. 
  citrinum, 
  Sowerby, 
  costatum, 
  Sowb., 
  glolulus, 
  Sowb., 
  Proc. 
  

   Zool. 
  Soc. 
  Lond., 
  p. 
  50. 
  

  

  2. 
  Acanthina 
  luguhris 
  (Sowei'by). 
  

   1822. 
  Monoceros 
  luguhre, 
  J. 
  & 
  G. 
  B. 
  Sowerby, 
  Genera 
  No. 
  5, 
  

  

  pi. 
  ccxxxix, 
  f. 
  3, 
  

   1825. 
  M. 
  cymatum, 
  Sowerby, 
  Tankerv. 
  Cat., 
  No. 
  1888. 
  

   1828. 
  Buccimim 
  armatum, 
  Wood, 
  Suppl., 
  p. 
  12, 
  No. 
  12, 
  pi. 
  iv 
  (Biicc), 
  

  

  f. 
  12. 
  

   1835. 
  Monoceros 
  cymatum, 
  Sowerbv, 
  Conch. 
  Illust., 
  sp. 
  6, 
  pi. 
  Ixxxii. 
  

  

  f. 
  11. 
  

   1835. 
  M. 
  cymatum, 
  Sowerby, 
  Proc. 
  Zool. 
  Soc. 
  Lond., 
  p. 
  50. 
  

  

  Subgenus 
  Acanthinucella, 
  n. 
  

  

  1. 
  Acanthinucella 
  pimctulata 
  (Sowerby). 
  

  

  1835. 
  Monoceros 
  pmictulatum, 
  Sowerby, 
  Proc. 
  Zool. 
  Soc. 
  Lond., 
  p. 
  50. 
  

  

  1835. 
  M. 
  pmictulatum, 
  Sowerby, 
  Conch. 
  Illust., 
  sp. 
  13, 
  pi. 
  Ixxix, 
  

  

  f. 
  3. 
  

   1837. 
  Purpura 
  (Monoceros) 
  lapilloides, 
  Conrad, 
  Journ. 
  Acad. 
  Nat. 
  Sci. 
  

   Philad., 
  vii, 
  p. 
  265, 
  pi. 
  xx, 
  f. 
  18. 
  

  

  