﻿784 
  PROVEEDINdS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.xx. 
  

  

  This 
  genus 
  appears 
  to 
  be 
  closely 
  allied 
  to 
  Montacuta, 
  but 
  differs 
  in 
  

   not 
  having 
  a 
  definite, 
  raised, 
  posterior 
  tooth; 
  in 
  having 
  a 
  large, 
  elon- 
  

   gated 
  posterior 
  cartilage, 
  bearing 
  a 
  large 
  ossicle 
  attached 
  to 
  a 
  special 
  

   groove 
  nloiig 
  a 
  tooth-like 
  ridge; 
  and 
  in 
  having 
  the 
  structure 
  of 
  the 
  

   hinge 
  in 
  both 
  valves 
  nearly 
  the 
  same. 
  In 
  the 
  position 
  of 
  the 
  resiliuni 
  

   it 
  resembles 
  Erycina, 
  but 
  the 
  latter 
  has 
  two 
  large 
  teeth 
  in 
  both 
  valves. 
  

  

  KELLIOPSIS 
  ELEVATA 
  (Stimpson). 
  

  

  (Plates 
  XCIII, 
  figs. 
  2-4; 
  XCIV, 
  figs. 
  7, 
  8.) 
  

  

  MontacKta 
  hUlentaia 
  Gottld, 
  Rep. 
  on 
  Invert, 
  of 
  Mass., 
  1st 
  ed., 
  p. 
  59, 
  1841. 
  (Not 
  

  

  of 
  Moutagu.j 
  

   Montacuia 
  ilerata 
  Stimpson, 
  Shells 
  of 
  Now 
  P^ug., 
  p. 
  16, 
  18.51. 
  

   Cyamium 
  elevatum 
  H. 
  and 
  A. 
  Adams, 
  Gener.i 
  Recent 
  Moll., 
  II, 
  p. 
  477, 
  1858. 
  

   Montacuia 
  elevata 
  Gocld, 
  Rep. 
  on 
  Invert, 
  of 
  Mass., 
  Binuey's 
  ed., 
  p. 
  86, 
  fig. 
  396, 
  

  

  1870.— 
  Tryon, 
  Amer. 
  Mar. 
  Couch., 
  p. 
  172, 
  pi. 
  xxxiii, 
  fig. 
  440, 
  1873.— 
  Verrill, 
  

  

  Report 
  Invert. 
  Anini. 
  of 
  Vineyard 
  Sd., 
  in 
  1st 
  Rep. 
  U. 
  S. 
  Fish 
  Com., 
  pp. 
  394, 
  

  

  68«, 
  1874 
  (aiith. 
  cop., 
  p. 
  418). 
  

   Tellimya 
  elerata 
  Dall, 
  Bull. 
  U. 
  S. 
  Nat. 
  Mns., 
  No. 
  37, 
  p. 
  50, 
  pi. 
  Lxviii, 
  fig. 
  6 
  (as 
  

  

  Montacuia 
  elevata 
  Stimpson), 
  1889. 
  

  

  This 
  rare 
  species 
  has 
  been 
  obtained 
  at 
  low-water 
  mark, 
  at 
  Savin 
  

   Eock, 
  near 
  Xew 
  Haven, 
  Connecticut 
  (J. 
  E. 
  Todd), 
  1871; 
  Wellfleet, 
  

   Massachusetts 
  (Webster), 
  1879; 
  Woods 
  Hole, 
  Massachusetts 
  (Gut 
  of 
  

   Canso), 
  1882; 
  Naushon 
  Island 
  (Gutters 
  and 
  Sheep 
  Pen 
  Cove), 
  1882; 
  

   and 
  Narragansett 
  Bay, 
  in 
  8i 
  to 
  10 
  fathoms, 
  1880. 
  

  

  Family 
  DIPLODONT1DJ5. 
  

  

  Ungulinidw 
  Fischer; 
  l)iplodontid<v 
  -{- 
  Cri/ptodoiitida- 
  Dall. 
  

   CRYPTODON 
  Turton, 
  1822. 
  

  

  Type. 
  — 
  Cryptodon 
  ffexuosus 
  (Montagu). 
  

  

  The 
  typical 
  species 
  of 
  this 
  genus 
  have 
  no 
  distinct 
  teeth 
  in 
  either 
  valve, 
  

   but 
  tlie 
  inner 
  margin 
  of 
  the 
  hinge-plate 
  is 
  more 
  or 
  less 
  thickened 
  or 
  

   swollen 
  in 
  front 
  of 
  and 
  beliiud 
  the 
  beaks. 
  The 
  ligament 
  is 
  posterior 
  and 
  

   lies 
  in 
  a 
  long, 
  curved 
  furrow 
  in 
  the 
  midst 
  of 
  the 
  marginal 
  thickening; 
  

   where 
  it 
  (;ommences 
  at 
  the 
  beak 
  it 
  is 
  marginal 
  and 
  external, 
  but 
  as 
  it 
  

   runs 
  backward 
  it 
  recedes 
  from 
  the 
  edge 
  and 
  becomes 
  more 
  or 
  less 
  

   internal 
  and 
  invisible 
  from 
  the 
  exterior. 
  Moreover, 
  the 
  posterior 
  end 
  

   of 
  the 
  shell 
  has 
  one 
  or 
  more 
  distinct 
  radial 
  corrugations 
  or 
  plications 
  

   to 
  give 
  the 
  thin 
  shell 
  strength 
  enough 
  to 
  resist 
  the 
  action 
  of 
  the 
  large 
  

   posterior 
  adductor 
  muscle 
  which 
  is 
  attached 
  directly 
  upon 
  the 
  princi- 
  

   pal 
  plication. 
  The 
  pedal 
  muscle 
  is 
  attached 
  to 
  the 
  upi)er 
  i)lication 
  

   when 
  the 
  latter 
  is 
  present. 
  Many 
  writers 
  have 
  adopted 
  the 
  name 
  of 
  

   Axinns 
  Sowerby, 
  1823, 
  for 
  this 
  genus; 
  the 
  latter 
  name 
  was 
  given 
  to 
  a 
  

   tertiary 
  species, 
  the 
  structure 
  of 
  which 
  is 
  not 
  fully 
  determined. 
  It 
  may 
  

   belong 
  to 
  a 
  very 
  distinct 
  genus. 
  Moreover, 
  Turton's 
  name 
  seems 
  to 
  

   have 
  actual 
  priority 
  of 
  publication. 
  

  

  