﻿which 
  inhabit 
  Jamaica. 
  85 
  

  

  Named 
  in 
  honor 
  of 
  the 
  Honorable 
  Mr. 
  Roberts 
  of 
  Jamaica, 
  

   to 
  whom 
  we 
  are 
  indebted 
  for 
  this 
  and 
  other 
  interesting 
  species. 
  

  

  Cylindrella 
  rosea, 
  var. 
  fortis. 
  Shell 
  as 
  long 
  as 
  var. 
  ma- 
  

   jo?', 
  (p. 
  21,) 
  but 
  with 
  less 
  diameter 
  and 
  more 
  cylindric. 
  

  

  Cylindrella 
  zonata. 
  Shell 
  cylindric 
  in 
  the 
  lower 
  twj- 
  

   thirds, 
  very 
  robust 
  : 
  pinlc 
  witli 
  a 
  tinge 
  of 
  brown 
  or 
  purple, 
  

   with 
  a 
  pearl 
  white 
  zone 
  along 
  the 
  suture 
  ; 
  pale 
  brown 
  in 
  tho 
  

   aperture 
  : 
  with 
  an 
  elegant 
  silky 
  lustre 
  produced 
  by 
  crowded 
  

   oblique 
  very 
  fine 
  striae 
  : 
  spire 
  with 
  the 
  outlines 
  convex 
  in 
  their 
  

   upper 
  half; 
  apex 
  truncate 
  with 
  the 
  loss 
  of 
  — 
  whorls 
  : 
  whorls 
  

   remaining 
  eight, 
  moderately 
  convex, 
  slightly 
  margined 
  on 
  the 
  

   lower 
  side, 
  with 
  a 
  moderately 
  impressed 
  suture 
  : 
  aperture 
  

   similar 
  to 
  that 
  of 
  C. 
  rosea, 
  but 
  more 
  dilated 
  in 
  the 
  lower 
  part 
  

   of 
  the 
  leftside, 
  and 
  with 
  the 
  lip 
  less 
  expanded. 
  It 
  resembles 
  

   C 
  cylindrus, 
  but 
  differs 
  in 
  always 
  having 
  a 
  white 
  zone, 
  and 
  

   in 
  being 
  often 
  tinged 
  with 
  brown 
  ; 
  it 
  is 
  much 
  more 
  robust 
  : 
  the 
  

   aperture 
  of 
  C. 
  cylindrus 
  is 
  more 
  like 
  that 
  of 
  C. 
  rosea 
  than 
  of 
  

   this 
  shell. 
  

  

  Length 
  1.18 
  inch 
  ; 
  breadth 
  .41 
  inch. 
  

  

  Cylindrella 
  lata 
  often 
  occurs 
  with 
  a 
  much 
  elongate 
  sub- 
  

   conic 
  form. 
  This 
  variety 
  may 
  be 
  designated 
  by 
  the 
  name 
  

   PRODucTA. 
  A 
  specimen 
  is 
  1.23 
  inch 
  long 
  and 
  .34 
  inch 
  broad. 
  

  

  Under 
  Cylindrella 
  Maugeri 
  may 
  be 
  comprehended 
  many 
  

   types, 
  which 
  differ 
  in 
  color, 
  form, 
  and 
  sculpture. 
  These 
  vari- 
  

   eties 
  are 
  very 
  local, 
  being 
  strictly 
  limited 
  to 
  their 
  several 
  dis- 
  

   tricts. 
  But 
  many 
  of 
  these 
  districts 
  have 
  two 
  varieties. 
  They 
  

   all 
  conform 
  with 
  great 
  exactness 
  to 
  a 
  common 
  type, 
  which 
  is 
  

   of 
  much 
  less 
  than 
  generic 
  value. 
  The 
  very 
  considerable 
  num- 
  

   bers 
  of 
  each 
  variety, 
  their 
  strict 
  conformity 
  to 
  their 
  respective 
  

   subtypes, 
  and 
  their 
  geographical 
  distribution, 
  seem 
  to 
  indicate 
  

   a 
  specific 
  value 
  in 
  the 
  differences 
  between 
  them. 
  Yet 
  the 
  

   number 
  of 
  types 
  is 
  so 
  great 
  and 
  the 
  differences 
  between 
  many 
  

   of 
  them 
  are 
  so 
  slight, 
  that 
  we 
  may 
  well 
  hesitate 
  to 
  pronounce 
  

  

  MAY, 
  1851. 
  7 
  

  

  