﻿832 
  riiOCEEDIXGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.xx. 
  

  

  CYCLOPECTEN 
  Verrill, 
  1897. 
  

  

  C>jdoi)ecUn\¥AiiiU.\., 
  Trans. 
  Coim. 
  Acad., 
  X, 
  pp. 
  70, 
  90, 
  !t2, 
  \)\. 
  xvi, 
  lij;. 
  1; 
  pi. 
  

   XIX, 
  fio-s. 
  1-4, 
  1897. 
  

  

  Types. 
  — 
  Cyclopecten 
  pustulosus 
  Verrill 
  siiid 
  (Jyclopeeten 
  inihrifer 
  

   (Lovf'fi). 
  

  

  Shells 
  tbin, 
  rounded, 
  scarcely 
  oblique, 
  with 
  symmetrical 
  auricles 
  and 
  

   simple 
  margins. 
  The 
  two 
  valves 
  are 
  uulike 
  in 
  sculpture. 
  The 
  right 
  

   valve 
  is 
  a 
  little 
  flattened 
  and 
  upturned 
  at 
  the 
  flexible 
  margin, 
  so 
  as 
  to 
  

   fit 
  tightly 
  against 
  the 
  upper 
  valve. 
  Tlie 
  thin 
  lower 
  valve 
  has, 
  in 
  the 
  

   typical 
  species, 
  regular, 
  thin, 
  elevated, 
  concentric 
  lamellse, 
  which 
  aid 
  

   in 
  the 
  adaptation 
  of 
  the 
  edge 
  to 
  that 
  of 
  the 
  upper 
  valve; 
  the 
  margin 
  is 
  

   usually 
  flattened 
  or 
  bevelled. 
  The 
  upper 
  (left) 
  valve 
  is 
  radially 
  sculp- 
  

   tured, 
  rarely 
  smooth; 
  it 
  usually 
  has 
  radial 
  rows 
  of 
  arched 
  scales, 
  

   pustules, 
  or 
  points, 
  and 
  also 
  concentric 
  raised 
  lines; 
  it 
  is 
  sometimes 
  

   cancellated. 
  No 
  radial 
  ribs, 
  nor 
  interlocking 
  points 
  at 
  the 
  margin. 
  

   Auricles 
  well-de^'eloped, 
  subequal, 
  angulated 
  and 
  well 
  defined 
  at 
  both 
  

   ends; 
  byssal 
  notch 
  well 
  defined 
  ; 
  few 
  or 
  no 
  pectinidial 
  teeth. 
  Cardinal 
  

   folds 
  single, 
  rather 
  feebly 
  developed, 
  often 
  cross-lined. 
  Eyes 
  few. 
  

   Byssus 
  small, 
  and 
  of 
  few 
  threads. 
  

  

  This 
  genus 
  includes 
  a 
  large 
  number 
  of 
  small 
  si^ecies, 
  mostly 
  from 
  

   deep-water. 
  

  

  HTALOPECTEN 
  Verrill, 
  1897. 
  

   Hyalopecteti 
  Verkill, 
  Trans. 
  Conn. 
  Acad., 
  X, 
  pp. 
  71,00, 
  !)2, 
  pi. 
  x^iii, 
  lig. 
  5, 
  1897. 
  

  

  Typi-. 
  — 
  Hyalopecten 
  undaius 
  Verrill. 
  

  

  Shell 
  compressed, 
  thin, 
  hyaline. 
  Valves 
  nearly 
  equal, 
  with 
  concen- 
  

   tric 
  undulations 
  or 
  corrugations, 
  affecting 
  the 
  entire 
  thickness; 
  mar- 
  

   gins 
  simple; 
  sculpture 
  none, 
  or 
  consisting 
  of 
  fine 
  radial 
  lines 
  on 
  one 
  or 
  

   both 
  valves, 
  Avithout 
  camptonectes 
  sculpture. 
  Hinge-plate 
  thin 
  and 
  

   nearly 
  plain; 
  auricles 
  well-developed, 
  unequal; 
  byssal 
  notch 
  distinct. 
  

  

  For 
  the 
  possible 
  relations 
  of 
  this 
  group 
  to 
  the 
  Mesozoic 
  genus, 
  iSyncy- 
  

   clonema, 
  see 
  the 
  original 
  article. 
  

  

  The 
  species 
  recorded 
  are 
  as 
  follows: 
  H. 
  dileetns 
  Yerrill 
  and 
  Bush, 
  

   from 
  1,813 
  fathoms, 
  off 
  Marthas 
  Vineyard; 
  H. 
  fray 
  ills 
  (Jeffreys), 
  from 
  

   northern 
  Europe 
  and 
  the 
  Arctic 
  Ocean, 
  and 
  off 
  the 
  United 
  States 
  

   coast, 
  in 
  578 
  to 
  1,525 
  fathoms; 
  H. 
  undatus 
  Verrill, 
  off 
  the 
  United 
  

   States 
  coast, 
  in 
  1,423 
  fathoms; 
  and 
  H. 
  pudicus 
  (Smith), 
  oft" 
  Marion 
  

   Island, 
  in 
  1,375 
  fathoms. 
  

  

  PARAMUSIUM 
  Verrill, 
  1897. 
  

   Paramiisinm 
  Verrill, 
  Trans. 
  (Jonn. 
  Acad., 
  X, 
  pp. 
  72, 
  90, 
  92, 
  1897. 
  

  

  Type. 
  — 
  Paramusium 
  dalli 
  (Smith).' 
  

  

  Shell 
  thin, 
  rounded, 
  much 
  compressed; 
  valves 
  nearly 
  equal; 
  sculp- 
  

   ture 
  nearly 
  obsolete, 
  different 
  on 
  the 
  two 
  valves; 
  the 
  lower 
  valve 
  with 
  

   concentric 
  undulations. 
  Auricles 
  very 
  small, 
  equal. 
  Byssal 
  notch 
  and 
  

  

  ip. 
  dalli 
  ranges 
  from 
  the 
  Gulf 
  of 
  Mexico 
  to 
  Barbados, 
  in 
  218 
  to 
  1,591 
  fathoms. 
  

  

  