﻿Analysis 
  of 
  a 
  certain 
  Group 
  of 
  Species 
  of 
  Cyclostoma. 
  59 
  

  

  the 
  descriptions 
  of 
  both 
  authors 
  exclude 
  an 
  umbilical 
  keel. 
  

   No. 
  3 
  has 
  the 
  same 
  general 
  form 
  as 
  the 
  figure 
  of 
  C. 
  subrugo- 
  

   sum, 
  but 
  wants 
  the 
  umbilical 
  keel. 
  This 
  species 
  we 
  are 
  una- 
  

   ble 
  to 
  identify. 
  The 
  following 
  nomenclature 
  is 
  proposed 
  : 
  

   No. 
  1. 
  Cyclostoma 
  corrugatum 
  ? 
  Sowb. 
  

  

  2. 
  Cyclostoma 
  jugosum 
  Ad. 
  sp. 
  nov, 
  

  

  3. 
  Cyclostoma 
  pallescens 
  Ad. 
  sp. 
  nov. 
  

   5-14. 
  Cyclostoma 
  varians 
  Ad. 
  sp. 
  nov. 
  

   15. 
  Cyclostoma 
  seminudum 
  Ad. 
  sp. 
  nov. 
  

   16-18. 
  Cyclostoma 
  Jamaicense 
  Chem. 
  

   19. 
  Cyclostoma 
  crassum 
  Ad. 
  sp. 
  nov. 
  

  

  ' 
  It 
  will 
  be 
  seen 
  that 
  we 
  have 
  made 
  much 
  use 
  of 
  the 
  oper- 
  

   culum. 
  The 
  differences 
  of 
  this 
  part 
  appear 
  in 
  this 
  group 
  to 
  

   be 
  more 
  constant 
  and 
  better 
  defined 
  than 
  those 
  of 
  the 
  shell. 
  

   They 
  are 
  evidently 
  of 
  value 
  in 
  distinguishing 
  species 
  and 
  even 
  

   groups 
  which 
  are 
  somewhat 
  more 
  comprehensive 
  than 
  species. 
  

   We 
  would, 
  however, 
  with 
  M. 
  Petit 
  and 
  Mr. 
  Redfield, 
  stop 
  far 
  

   short 
  of 
  assigning 
  a 
  generic 
  value 
  to 
  the 
  differences 
  in 
  the 
  

   opercula 
  of 
  the 
  groups 
  of 
  Cyclostoma. 
  

  

  No. 
  1. 
  Shell 
  reddish 
  in 
  the 
  upper 
  whorls 
  ; 
  in 
  the 
  lower 
  whorls 
  pale 
  horn 
  color 
  

   or 
  din^y 
  white 
  ; 
  with 
  a 
  brown 
  epidermis 
  : 
  with 
  deep 
  transverse 
  somewhat 
  wrinkled 
  

   Btriee 
  on 
  all 
  the 
  whorls 
  ; 
  foveately 
  wrinkled, 
  with 
  shallow 
  depressions 
  ; 
  with 
  a 
  dis- 
  

   tinct 
  umbilical 
  keel, 
  and 
  large 
  curved 
  pits 
  exterior 
  to 
  the 
  keel 
  : 
  spire 
  well 
  elevated: 
  

   whorls 
  nearly 
  five, 
  flattened 
  on 
  the 
  upper 
  part, 
  with 
  a 
  well 
  impressed 
  suture 
  : 
  aper- 
  

   ture 
  suborbicular, 
  quite 
  effuse 
  and 
  pointed 
  above 
  ; 
  lip 
  sinuate 
  above, 
  much 
  ad- 
  

   vanced 
  along 
  the 
  middle 
  of 
  the 
  right 
  side, 
  naoderately 
  thickened: 
  umbilicus 
  a 
  

   little 
  more 
  than 
  half 
  as 
  wide 
  as 
  the 
  aperture. 
  Operculum 
  with 
  a 
  much 
  elevated 
  

   spiral 
  lamella 
  in 
  nine 
  whorls, 
  which 
  are 
  much 
  inflected 
  curvatelj', 
  the 
  outer 
  surface 
  

   being 
  convex, 
  like 
  the 
  sides 
  of 
  an 
  inverted 
  saucer. 
  

  

  Mean 
  divergence 
  120° 
  ; 
  height 
  .55 
  inch 
  ; 
  greatest 
  breadth 
  .88 
  inch 
  ; 
  least 
  

   breadth 
  .69 
  inch. 
  

  

  No. 
  2. 
  Shell 
  white, 
  with 
  a 
  light 
  brown 
  epidermis: 
  with 
  rather 
  deep 
  transverse 
  

   strise, 
  which 
  are 
  very 
  regular 
  on 
  the 
  upper 
  whorls, 
  and 
  very 
  irregular 
  on 
  the 
  last 
  

   whorl 
  : 
  with 
  deep 
  wrinkles 
  commencing 
  near 
  the 
  end 
  of 
  the 
  penult 
  whjrl, 
  where 
  

   they 
  are 
  somewhat 
  regular 
  and 
  oblique, 
  as 
  they 
  are 
  also 
  on 
  the 
  lower 
  side 
  of 
  the 
  

   last 
  whorl, 
  on 
  the 
  upper 
  side 
  of 
  which 
  they 
  are 
  irregular 
  and 
  knotty 
  ; 
  the 
  umbilical 
  

   keel 
  is 
  obsolete 
  : 
  spire 
  much 
  depressed 
  : 
  whorls 
  nearly 
  five, 
  well 
  rounded, 
  with 
  a 
  

  

  