﻿114 
  ON 
  THE 
  NAIADES, 
  _ 
  

  

  Read 
  before 
  the 
  American 
  Philosophical 
  Society, 
  April 
  ISth, 
  1834. 
  

  

  Lymitca 
  acuta. 
  Plate 
  XIX. 
  fig. 
  81. 
  

  

  Testa 
  elongato-turritd, 
  tenui, 
  Isevi, 
  fusco-nigricante 
  ; 
  spird 
  attenuata; 
  anfrac- 
  

   tibus 
  senis 
  ; 
  aperturd 
  subovatd. 
  

  

  Shell 
  elevated, 
  turrited, 
  thin, 
  smooth, 
  dark 
  brown 
  ; 
  spire 
  attenuate 
  ; 
  whorls 
  six 
  ; 
  

   aperture 
  subovate. 
  

  

  Hab. 
  pond 
  four 
  miles 
  north 
  of 
  Philadelphia. 
  

   Diam. 
  -3, 
  Length 
  *7 
  of 
  an 
  inch, 
  

  

  Remarks. 
  — 
  This 
  delicate 
  species, 
  although 
  attenuate, 
  is 
  not 
  so 
  much 
  

   so 
  as 
  the 
  exilis 
  herein 
  described. 
  Its 
  whorls 
  are 
  more 
  convex 
  and 
  the 
  

   body 
  whorl 
  larger, 
  the 
  aperture 
  being 
  about 
  one 
  half 
  the 
  length 
  of 
  the 
  

   shell. 
  Several 
  specimens 
  were 
  found 
  by 
  me 
  some 
  years 
  since, 
  in 
  a 
  

   very 
  small 
  pond 
  near 
  to 
  the 
  Falls 
  of 
  Schuylkill. 
  Since 
  then 
  this 
  pond 
  

   has 
  occasionally 
  dried 
  up, 
  and 
  I 
  have 
  not 
  been 
  able 
  to 
  find 
  others. 
  

   Although 
  there 
  are 
  other 
  ponds 
  near 
  to 
  this, 
  which 
  other 
  species 
  in- 
  

   habit, 
  I 
  have 
  never 
  been 
  able 
  to 
  discover 
  the 
  acuta 
  in 
  any 
  other 
  spot. 
  

  

  Lymnjea 
  exilis. 
  Plate 
  XIX. 
  fig. 
  82. 
  

  

  Testa 
  attenuata, 
  tenuissimd, 
  longitudinaliter 
  striata; 
  anfractibus 
  septenis, 
  

   plano-convexis 
  ; 
  columella 
  reflexd; 
  aperturd 
  ovato-oblongd. 
  

  

  Shell 
  attenuated, 
  very 
  thin, 
  longitudinally 
  striate 
  ; 
  whorls 
  seven, 
  plano-convex 
  ; 
  

   columella 
  reflected 
  ; 
  aperture 
  ovato-oblong. 
  

  

  Hab. 
  Ohio, 
  T. 
  G. 
  Lea. 
  

  

  My 
  Cabinet. 
  

   Diam. 
  «4, 
  Length 
  1*5 
  inches. 
  

  

  