﻿BEEF- 
  WA 
  TER 
  MOLL 
  USCA— 
  TERBILL 
  A 
  XD 
  B 
  USE. 
  841 
  

  

  covered 
  with 
  small, 
  close, 
  radial 
  ribs 
  and 
  crowded 
  concentric 
  ridges; 
  

   l^osterior 
  auri(;le 
  much 
  smaller, 
  with 
  from 
  one 
  to 
  three 
  faint, 
  radial 
  

   ridi^es 
  and 
  many 
  concentric, 
  raised 
  lines, 
  and 
  with 
  its 
  outer 
  end 
  form- 
  

   ing 
  less 
  than 
  a 
  right 
  angle, 
  with 
  a 
  slight 
  incurved 
  notch 
  below. 
  In 
  

   the 
  right 
  valve 
  the 
  anterior 
  auricle 
  has 
  a 
  similar 
  radial 
  sculpture 
  and 
  

   the 
  byssal 
  notch 
  is 
  rather 
  deep 
  and 
  narrow. 
  The 
  dorsal 
  lines 
  of 
  the 
  

   body 
  of 
  the 
  shell 
  form 
  rather 
  less 
  than 
  a 
  right 
  angle; 
  the 
  ventral 
  mar- 
  

   gin 
  forms 
  nearly 
  a 
  semicircle 
  with 
  an 
  obtuse 
  angle 
  where 
  it 
  meets 
  the 
  

   dorsal 
  outline. 
  Umbos 
  a 
  little 
  prominent; 
  beaks 
  small, 
  acute, 
  smooth, 
  

   and 
  projecting 
  beyond 
  the 
  margin 
  of 
  the 
  hinge. 
  The 
  surface 
  of 
  the 
  

   left 
  valve 
  is 
  covered 
  with 
  slightly 
  raised 
  concentric 
  lines, 
  which 
  are 
  

   interrupted 
  or 
  broken 
  up 
  by 
  small 
  arched 
  scales 
  which 
  are 
  sometimes 
  

   semicircular, 
  but 
  more 
  frequently 
  somewhat 
  angulated 
  or 
  V-shaped, 
  

   and 
  usually 
  are 
  separated 
  by 
  intervals 
  about 
  equal 
  to 
  their 
  breadth 
  ; 
  

   these 
  scales 
  vary 
  in 
  number, 
  but 
  are 
  usually 
  arranged 
  in 
  about 
  forty 
  

   radial 
  rows, 
  and 
  increase 
  regularly 
  in 
  size 
  from 
  the 
  umbos, 
  where 
  they 
  

   are 
  replaced 
  by 
  thin, 
  slightly 
  raised, 
  radial 
  lines 
  crossing 
  the 
  stronger, 
  

   more 
  elevated, 
  concentric 
  lines, 
  but 
  not 
  rising 
  into 
  jioints. 
  In 
  some 
  

   specimens 
  the 
  radial 
  arrangement 
  is 
  scarcely 
  discernible; 
  the 
  scales 
  

   appear 
  as 
  irregularities 
  in 
  the 
  concentric 
  lines. 
  The 
  postero 
  dorsal 
  

   area 
  below 
  the 
  auricle 
  is 
  nearly 
  smooth, 
  except 
  for 
  the 
  hue 
  lines 
  of 
  

   growth, 
  but 
  sometimes 
  shows 
  minute 
  granules. 
  The 
  right 
  valve, 
  which 
  

   is 
  smaller 
  than 
  the 
  left, 
  is 
  covered 
  by 
  fine, 
  thin, 
  close, 
  concentric, 
  

   raised 
  lines, 
  which 
  sometimes 
  show 
  microscopic 
  striations. 
  The 
  ante- 
  

   rior 
  auricle 
  is 
  decussated 
  by 
  from 
  six 
  to 
  eight, 
  or 
  more, 
  small 
  radial 
  

   ridges, 
  which 
  are 
  crossed 
  by 
  the 
  raised, 
  concentric 
  lines; 
  the 
  latter 
  rise 
  

   into 
  sharp 
  scales 
  at 
  the 
  dorsal 
  margin 
  ; 
  the 
  small 
  posterior 
  auricle 
  has 
  

   finer 
  concentric 
  lines 
  and 
  only 
  two 
  or 
  three 
  faint, 
  radial 
  ridges. 
  

  

  Comparatively 
  few 
  specimens, 
  at 
  three 
  stations, 
  between 
  X. 
  lat. 
  42° 
  

   45' 
  30", 
  W. 
  long. 
  02° 
  4:V, 
  and 
  N. 
  lat. 
  39° 
  53' 
  30", 
  W. 
  long. 
  71° 
  13' 
  30", 
  

   in 
  121 
  to 
  312 
  fathoms, 
  1877-1885. 
  

  

  (J. 
  Jxcrmadecensis 
  (Smith), 
  from 
  north 
  of 
  Kermadec 
  Islands, 
  in 
  GOO 
  

   fathoms, 
  is 
  a 
  related 
  species. 
  

  

  PROPEAMUSIUM 
  THALASSINUM 
  (Dall) 
  Verrill. 
  

  

  (Plate 
  LXXX 
  VII, 
  fig. 
  6.) 
  

  

  Amussium 
  fenestratam 
  Verrill, 
  Trans. 
  Coun. 
  Acad., 
  V, 
  p. 
  582, 
  1882. 
  

  

  Amiissium 
  sp. 
  Verrill, 
  Traus. 
  Com. 
  Acad,, 
  VI, 
  pp. 
  261, 
  281, 
  1884. 
  

  

  Fecteii 
  (I'-teKdavuisium) 
  thalaiisinHS 
  Dall, 
  Bull. 
  Mus. 
  Comp. 
  Zool., 
  XII. 
  p. 
  221, 
  1886; 
  

  

  Bull. 
  U. 
  S. 
  Nat. 
  Mns.. 
  No. 
  37, 
  p. 
  31, 
  1889. 
  

   rropeamiisiHtn 
  ilialassinuvi 
  Verrill, 
  Traus. 
  Couu. 
  Acad., 
  X, 
  pp. 
  .S7, 
  i)2, 
  i>]. 
  xix, 
  

  

  figs..-)-?, 
  1897. 
  

  

  Found 
  at 
  thirteen 
  stations, 
  between 
  N. 
  lat. 
  40° 
  5' 
  39", 
  W. 
  long. 
  70° 
  

   23' 
  52", 
  and 
  N. 
  lat. 
  35° 
  42', 
  W. 
  long. 
  74° 
  54' 
  30", 
  in 
  43 
  to 
  317 
  fathoms, 
  

   1880-1885. 
  South 
  to 
  Barbados, 
  in 
  22 
  to 
  317 
  fathoms.— 
  Dall. 
  

  

  