﻿which 
  inhabit 
  Jamaica. 
  47 
  

  

  cept 
  on 
  the 
  upper 
  whorls 
  : 
  with 
  twelve 
  spiral 
  prominent 
  cord- 
  

   like 
  ridges, 
  half 
  of 
  which 
  appear 
  on 
  the 
  spire, 
  decussated 
  by 
  

   much 
  less 
  prominent 
  regular 
  transverse 
  ridges, 
  with 
  the 
  inter- 
  

   sections 
  well 
  developed 
  into 
  nodules': 
  apex 
  acute: 
  spire 
  with 
  

   the 
  outlines 
  moderately 
  curvilinear 
  : 
  whorls 
  five, 
  rather 
  con- 
  

   vex, 
  with 
  the 
  suture 
  moderately 
  impressed 
  ; 
  last 
  whorl 
  but 
  

   little 
  ventricose 
  : 
  aperture 
  rather 
  narrow 
  and 
  sinuous 
  ; 
  lip 
  

   slightly 
  thickened, 
  not 
  denticulate 
  within, 
  (in 
  old 
  shells 
  ?) 
  

   with 
  the 
  notch 
  of 
  medium 
  size. 
  

  

  Mean 
  divergence 
  about 
  40° 
  ; 
  length 
  .145 
  inch 
  ; 
  breadth 
  

   .06 
  inch 
  ; 
  length 
  of 
  aperture 
  .06 
  inch. 
  

  

  Of 
  Pleurotoma 
  albella 
  Ad., 
  (Cont. 
  to 
  Conch., 
  p. 
  63,) 
  a 
  va- 
  

   riety 
  is 
  wax-colored 
  at 
  both 
  extremities, 
  and 
  has 
  irregular 
  

   spiral 
  lines 
  of 
  the 
  same 
  on 
  the 
  lower 
  part 
  of 
  the 
  whorls. 
  

  

  Yalvata 
  inconspicua. 
  Shell 
  subdiscoidal 
  : 
  pale 
  horn 
  color 
  ? 
  

   with 
  the 
  striae 
  of 
  growth 
  microscopic 
  : 
  spire 
  convex, 
  moder- 
  

   ately 
  elevated 
  : 
  whorls 
  three, 
  very 
  rapidly 
  increasing, 
  with 
  a 
  

   deep 
  canaliculate 
  suture 
  : 
  aperture 
  large, 
  not 
  much 
  advanced 
  

   above 
  : 
  umbilicus 
  about 
  half 
  as 
  wide 
  as 
  the 
  penult 
  whorl. 
  

  

  Greatest 
  breadth 
  .07 
  inch 
  ; 
  least 
  breadth 
  .05 
  inch 
  ; 
  height 
  

   .04 
  inch. 
  

  

  Planorbis 
  humilis. 
  Shell 
  subdiscoidal 
  : 
  color 
  — 
  ? 
  with 
  

   coarse 
  striae 
  of 
  growth 
  : 
  apex 
  and 
  spire 
  moderately 
  depressed 
  

   on 
  the 
  right 
  side 
  : 
  whorls 
  two 
  and 
  one-half; 
  last 
  whorl 
  with 
  

   a 
  very 
  acute 
  periphery 
  nearly 
  in 
  the 
  plane 
  of 
  the 
  spire, 
  mod- 
  

   erately 
  dilated 
  around 
  the 
  umbilical 
  region 
  : 
  aperture 
  large, 
  

   subtriangular, 
  acutely 
  angled 
  at 
  the 
  periphery 
  of 
  the 
  last 
  

   whorl 
  : 
  umbilical 
  region 
  abruptly 
  excavated, 
  with 
  the 
  conca- 
  

   vity 
  about 
  two-thirds 
  as 
  wide 
  as 
  the 
  last 
  whorl. 
  

  

  Greatest 
  breadth 
  .06 
  inch 
  ; 
  least 
  breadth 
  .045 
  inch 
  ; 
  height 
  

   .025 
  inch. 
  

  

  