﻿Analysis 
  of 
  a 
  certain 
  Group 
  of 
  Species 
  of 
  Cyclostoma. 
  61 
  

  

  panded 
  in 
  both 
  directions 
  but 
  mostly 
  on 
  the 
  exterior, 
  and 
  is 
  then 
  carved 
  down- 
  

   wards, 
  presenting 
  a 
  broad 
  rounded 
  summit. 
  A 
  transverse 
  section 
  of 
  the 
  lamina 
  

   somewhat 
  resembles 
  the 
  italic 
  letter 
  T. 
  

  

  Mean 
  divergence 
  about 
  120° 
  ; 
  height 
  .46 
  inch 
  ; 
  greatest 
  breadth 
  .84 
  inch 
  ; 
  

   'east 
  breadth 
  .65 
  inch. 
  

  

  No. 
  7. 
  This 
  differs 
  from 
  No. 
  6: 
  the 
  depression 
  of 
  the 
  last 
  whorl 
  above 
  is 
  rather 
  

   deeper, 
  and 
  extends 
  along 
  the 
  penult 
  whori 
  where 
  it 
  is 
  linear 
  ; 
  the 
  wrinkles 
  are 
  

   less 
  regular, 
  and 
  are 
  often 
  wanting 
  at 
  the 
  end 
  atid 
  lower 
  side 
  of 
  the 
  penult 
  whori 
  ; 
  

   the 
  umbilical 
  keel 
  is 
  very 
  strongly 
  developed 
  ; 
  the 
  epidermis 
  is 
  very 
  dark 
  brown 
  ; 
  

   in 
  the 
  whoris 
  of 
  the 
  opercular 
  lamina, 
  the 
  lateral 
  expansions 
  come 
  in 
  contact, 
  form- 
  

   ing 
  a 
  covered 
  way 
  beneath. 
  This 
  type 
  inhabits 
  the 
  parish 
  of 
  Portland. 
  It 
  attams 
  

   a 
  great 
  size 
  and 
  solidity. 
  

  

  Mean 
  divergence 
  about 
  120°; 
  height 
  .85 
  inch; 
  greatest 
  breadth 
  1.36 
  inch 
  ; 
  

   least 
  breadth 
  1.05 
  inch. 
  

  

  No. 
  8 
  differs 
  from 
  the 
  preceding, 
  in 
  having 
  the 
  whole 
  surface 
  destitute 
  of 
  wrm- 
  

   kles. 
  

  

  No. 
  9 
  is 
  also 
  like 
  No. 
  7 
  ; 
  but 
  its 
  operculum 
  is 
  flatter, 
  and 
  has 
  two 
  more 
  whoris, 
  

   and 
  all 
  its 
  whoris 
  are 
  therefore 
  narrower 
  ; 
  the 
  epidermis 
  is 
  light 
  brown 
  ; 
  and 
  the 
  

   wrinkles 
  are 
  neariy 
  obsolete, 
  except 
  a 
  few 
  which 
  are 
  small 
  and 
  well 
  defined 
  near 
  

   the 
  commencement 
  of 
  the 
  penult 
  whori. 
  

  

  Mean 
  divergence 
  130° 
  ; 
  height 
  .6 
  inch 
  ; 
  greatest 
  breadth 
  1.03 
  inch 
  ; 
  least 
  

   breadth 
  .81 
  inch. 
  

  

  No. 
  10. 
  The 
  wrinkles 
  are 
  well 
  developed, 
  rather 
  sharp, 
  oblique 
  and 
  regular 
  on 
  

   the 
  penult 
  and 
  antepenult 
  whorls, 
  and 
  are 
  neariy 
  obsolete 
  on 
  the 
  last 
  whori, 
  the 
  

   lower 
  side 
  of 
  which 
  is 
  quite 
  smooth 
  ; 
  the 
  umbilical 
  keel 
  is 
  very 
  prominent 
  ; 
  the 
  

   operculum 
  is 
  like 
  that 
  of 
  No. 
  9. 
  Some 
  have 
  a 
  few 
  raised 
  spiral 
  lines 
  on 
  the 
  last 
  

   whorl. 
  

  

  Mean 
  divergence 
  125° 
  ; 
  height 
  .55 
  inch 
  ; 
  greatest 
  breadth 
  .95 
  inch 
  ; 
  least 
  

   breadth 
  .75 
  inch. 
  

  

  No. 
  11. 
  White, 
  often 
  reddish 
  ; 
  the 
  epidermis 
  is 
  dark 
  brown, 
  with 
  a 
  white 
  stripe 
  

   next 
  below 
  the 
  suture 
  on 
  the 
  last 
  whori 
  : 
  with 
  the 
  transverse 
  striae 
  excessively 
  mi- 
  

   nute 
  : 
  the 
  wrinkles 
  are 
  very 
  small 
  on 
  the 
  antepenult 
  and 
  penult 
  whoris, 
  and 
  nearly 
  

   obsolete 
  on 
  the 
  upper 
  part 
  of 
  the 
  last 
  whorl, 
  which 
  is 
  smooth 
  below 
  ; 
  there 
  are 
  a 
  

   few 
  indistinct 
  spiral 
  stria; 
  ; 
  the 
  umbilical 
  keel 
  is 
  well 
  developed 
  : 
  spire 
  well 
  eleva- 
  

   ted 
  : 
  whoris 
  neariy 
  five, 
  slightly 
  depressed 
  above 
  ; 
  with 
  a 
  well 
  impressed 
  suture 
  : 
  

   aperture 
  suborbicular, 
  quite 
  pointed 
  and 
  effuse 
  above 
  ; 
  lip 
  well 
  thickened, 
  much 
  

   advanced 
  on 
  the 
  right 
  side 
  : 
  umbilicus 
  half 
  as 
  wide 
  as 
  the 
  aperture. 
  Operculum- 
  

   like 
  that 
  of 
  No. 
  9. 
  

  

  Inhabits 
  St. 
  John's. 
  

  

  Mean 
  divergence 
  about 
  130° 
  ; 
  height 
  .55 
  inch 
  ; 
  greatest 
  breadth 
  .92 
  inch 
  i 
  

   least 
  breadth 
  .74 
  inch. 
  

  

  No. 
  12 
  differs 
  from 
  No. 
  11 
  in 
  having 
  the 
  whoris 
  more 
  flattened 
  above, 
  and 
  the 
  

   aperture 
  more 
  dilated. 
  Operculum 
  as 
  in 
  No. 
  9. 
  

   Inhabits 
  the 
  north 
  side, 
  in 
  St. 
  Mary's. 
  

  

  