﻿Ko.n39. 
  DEEP-WATEB 
  MOLLUSCA—TERBILL 
  AND 
  BUSH. 
  809' 
  

  

  CARDIOMYA 
  PERROSTRATA 
  Dall. 
  

   (Plates 
  LXXIII, 
  tig. 
  2; 
  LXXIV, 
  iig. 
  3.) 
  

  

  Kecera 
  perrosirata 
  Verrill, 
  Trans. 
  Conn. 
  Acad., 
  V, 
  p. 
  561, 
  1882 
  ; 
  YI, 
  p. 
  277, 
  1884. 
  

   Cardiomya 
  2)errosfrata 
  Dall, 
  Bull. 
  Miis. 
  Conip. 
  Zoul., 
  XII, 
  p. 
  296, 
  pi. 
  ii, 
  figs. 
  3a, 
  3b, 
  

   1886 
  ; 
  Bull. 
  U. 
  S. 
  Nat. 
  Mus., 
  No. 
  37, 
  p. 
  66, 
  pi. 
  ii, 
  figs. 
  3a, 
  3b, 
  1889. 
  

  

  Only 
  a 
  few 
  specimens 
  were 
  obtained 
  from 
  seven 
  stations 
  between 
  K. 
  

   lat. 
  40° 
  15' 
  30", 
  W. 
  long. 
  70° 
  27', 
  and 
  :N^. 
  lat. 
  39° 
  4G' 
  30", 
  W. 
  long. 
  70° 
  

   54', 
  in 
  58 
  to 
  325 
  fatlioms, 
  1S80-1884. 
  

  

  South 
  to 
  Granada, 
  in 
  339 
  to 
  41G 
  fathoms. 
  — 
  Dall. 
  

  

  CARDIOMYA 
  GEMMA, 
  new 
  species. 
  

   (Plates 
  LXXI, 
  figs. 
  3, 
  4; 
  LXXIV, 
  fig. 
  11.) 
  

  

  Necera 
  pmtcistriata 
  Bush, 
  Trans. 
  Conn. 
  Acad., 
  VI, 
  p. 
  473, 
  1885. 
  

  

  T^ot 
  Mijonera 
  pancistriata'DAi.i., 
  Bull. 
  Mus. 
  Comp. 
  Zool., 
  XII, 
  p. 
  302, 
  1886; 
  Bull. 
  

  

  U. 
  S. 
  Nat. 
  Mus., 
  No. 
  37, 
  p. 
  68, 
  1889 
  ; 
  Proc. 
  U. 
  S. 
  Nat. 
  Mus., 
  XII, 
  p. 
  233, 
  pi. 
  xiii, 
  fig. 
  

  

  12, 
  1889. 
  

   Cardioviya 
  sp. 
  Bush, 
  Bull. 
  Mus. 
  Comp. 
  ZoiU., 
  XXIII, 
  p. 
  227, 
  1893. 
  

  

  Shell 
  small, 
  inequivalved, 
  thin, 
  fragile, 
  translucent, 
  bluish 
  white, 
  

   somewhat 
  ovate, 
  with 
  a 
  well-defined 
  rostrum. 
  Umbos 
  smooth, 
  a 
  little 
  

   prominent; 
  the 
  beaks 
  small, 
  inconsjncuous. 
  Tbe 
  antero-dorsal 
  margin 
  

   is 
  convex 
  and 
  rises 
  distinctly 
  above 
  the 
  beaks 
  so 
  that 
  the 
  greatest 
  

   height 
  of 
  the 
  shell 
  is 
  in 
  front 
  of 
  them; 
  thence 
  it 
  slojies 
  rapidly 
  to 
  

   the 
  somewhat 
  prominent 
  anterior 
  end; 
  the 
  ventral 
  margin 
  is 
  broadly 
  

   rounded 
  with 
  a 
  slight 
  angle 
  at 
  the 
  termination 
  of 
  each 
  radial 
  rib, 
  

   decidedly 
  incurved 
  at 
  the 
  base 
  of 
  the 
  rostrum 
  which 
  is 
  a 
  little 
  elon- 
  

   gated, 
  nearly 
  straight, 
  somewhat 
  tapered, 
  and 
  rather 
  upturned 
  distally 
  ; 
  

   the 
  postero 
  dorsal 
  margin 
  is 
  depressed 
  and 
  somewhat 
  concave. 
  Each 
  

   valve 
  has 
  three 
  conspicuous, 
  prominent, 
  thin, 
  elevated, 
  distant, 
  radial 
  

   ribs 
  on 
  the 
  posterior 
  half 
  and 
  a 
  fourth 
  less 
  distinct 
  one 
  at 
  about 
  the 
  

   middle; 
  this 
  is 
  rudimentary 
  in 
  tbe 
  left 
  valve; 
  none 
  of 
  them 
  reach 
  the 
  

   umbos. 
  The 
  surface 
  is 
  also 
  covered 
  with 
  very 
  delicate 
  lines 
  of 
  growth; 
  

   the 
  rostrum 
  does 
  not 
  have 
  a 
  diagonal 
  ridge. 
  The 
  hinge-margin 
  is 
  thin 
  

   and 
  delicate; 
  the 
  right 
  valve 
  has 
  a 
  small 
  but 
  prominent, 
  moderately 
  

   long 
  lateral 
  tooth 
  separated 
  from 
  the 
  very 
  minute 
  cartilage-plate 
  by 
  a 
  

   distinct 
  notch. 
  The 
  lateral 
  tooth 
  is 
  supported 
  by 
  a 
  small 
  buttress. 
  

  

  Length, 
  5 
  mm.; 
  height, 
  3 
  mm. 
  

  

  A 
  few 
  specimens 
  ofi" 
  Cape 
  Hatteras, 
  North 
  Carolina, 
  in 
  10 
  and 
  17 
  

   fathoms, 
  1884. 
  

  

  