﻿842 
  I'llOVEEIUNiiS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  

  

  Family 
  AEOIDvE. 
  

  

  BATHYARCA 
  Kobelt. 
  

  

  Type. 
  — 
  Baihyarca 
  peetun 
  cii 
  lo 
  ides 
  ( 
  Scac-cbi 
  ) 
  . 
  

  

  Shell 
  oblong', 
  subovate, 
  or 
  louiidecl, 
  rather 
  thin, 
  usually 
  finely 
  can- 
  

   celhited, 
  with 
  hairy 
  or 
  scaly 
  epidermis, 
  more 
  or 
  less 
  equilateral, 
  tie 
  

   quentiy 
  slightly 
  inequivalved, 
  with 
  a 
  slight 
  byssal 
  sinus, 
  Byssus 
  very 
  

   small. 
  Ligamental 
  area 
  lanceolate, 
  longer 
  and 
  narrower 
  behind 
  the 
  

   beaks, 
  with 
  a 
  sagittate 
  posterior 
  ligament. 
  Ilinge-margiu 
  nearly 
  

   straight, 
  usually 
  narrow 
  and 
  edentulous 
  in 
  the 
  middle, 
  with 
  a 
  series 
  

   of 
  small, 
  oblique, 
  striated 
  and 
  crenulated 
  teeth 
  on 
  each 
  end, 
  the 
  distal 
  

   ones 
  becoming 
  larger 
  and 
  more 
  oblicjue; 
  those 
  of 
  the 
  posterior 
  series 
  

   usually 
  longer 
  and 
  more 
  oblique, 
  or 
  divergent, 
  than 
  those 
  in 
  the 
  

   anterior. 
  

  

  The 
  animal 
  of 
  7>. 
  pectunculoides 
  var. 
  grandis, 
  preserved 
  in 
  alcohol, 
  has 
  

   the 
  margin 
  of 
  the 
  mantle 
  plain 
  without 
  ocelli, 
  with 
  a 
  well-developed 
  

   nuiscnlar 
  septum, 
  posteriorly; 
  the 
  foot 
  large 
  and 
  thick, 
  geniculate, 
  

   pointed 
  posteriorly, 
  with 
  a 
  strong 
  byssal 
  groove 
  and 
  a 
  slender, 
  solid, 
  

   byssal 
  stem; 
  two 
  pairs 
  of 
  rather 
  small, 
  long, 
  lanceolate 
  palpi; 
  the 
  rec- 
  

   tum 
  with 
  a 
  free 
  terminal 
  portion; 
  two 
  pairs 
  of 
  rather 
  large 
  gills, 
  with 
  

   the 
  posterior 
  end 
  of 
  the 
  stem 
  free 
  for 
  some 
  distance, 
  curved, 
  and 
  

   tapered 
  to 
  a 
  point, 
  and 
  with 
  the 
  reflected 
  portion 
  of 
  the 
  filament 
  of 
  the 
  

   same 
  length 
  as 
  the 
  direct; 
  the 
  filaments 
  are 
  very 
  slender, 
  delicate, 
  and 
  

   soft 
  and 
  but 
  slightly 
  attached 
  to 
  each 
  other. 
  

  

  This 
  division, 
  which 
  is 
  j)robably 
  of 
  generic 
  value, 
  includes 
  a 
  number 
  

   of 
  small 
  and 
  mostly 
  deep-water 
  species 
  which 
  have 
  been 
  variously 
  

   placed 
  by 
  recent 
  authors. 
  Mr. 
  E. 
  A. 
  Smith 
  puts 
  several 
  of 
  them 
  in 
  

   kSeapharea 
  with 
  a 
  mark 
  of 
  doubt. 
  Mr. 
  Dall 
  puts 
  two 
  allied 
  species 
  in 
  

   the 
  Jurassic 
  genus 
  Macrodon,^ 
  with 
  which 
  they 
  do 
  not 
  seem 
  to 
  agree 
  

   very 
  closely, 
  and 
  mentions 
  the 
  affinity 
  of 
  others 
  to 
  Barhatia. 
  

  

  The 
  last 
  group 
  differs 
  in 
  the 
  stout, 
  rough 
  shell, 
  strongly 
  gaping 
  ven- 
  

   trally 
  for 
  the 
  large 
  byssus, 
  and 
  in 
  the 
  character 
  of 
  the 
  teeth 
  and 
  liga- 
  

   ment. 
  Scapharca 
  has 
  a 
  thick, 
  strongly 
  ribbed, 
  inequivalved 
  shell, 
  a 
  

   firm 
  byssus, 
  and 
  continuous, 
  strong, 
  lanceolate 
  ligament. 
  Macrodon 
  

   has, 
  on 
  the 
  posterior 
  hinge-plate 
  long, 
  divergent 
  lamelhie, 
  nearly 
  paral- 
  

   lel 
  with 
  the 
  dorsal 
  margin. 
  

  

  We 
  would 
  refer 
  the 
  following 
  species 
  to 
  Bathyarca. 
  — 
  B. 
  pectuncu- 
  

  

  1 
  The 
  two 
  West 
  ludiau 
  species 
  described 
  by 
  Mr. 
  Dall 
  as 
  Macrodon 
  aspei'ula 
  and 
  

  

  31. 
  sagrinata, 
  should, 
  perhaps, 
  form 
  a 
  separate 
  <>('im8, 
  characterized 
  by 
  the 
  fevr 
  very 
  

   oblique, 
  sublamellar, 
  jiosterior 
  teeth 
  and 
  several 
  smaller, 
  nearly 
  transverse 
  anterior 
  

   ones. 
  It 
  may 
  be 
  designated 
  as 
  Beniharca, 
  -with 
  Beniharca 
  asperula 
  as 
  the 
  type. 
  

  

  These 
  are 
  closely 
  related 
  to 
  one 
  of 
  llie 
  Eocene 
  fossil 
  species 
  {Area 
  adversidcntata), 
  

   ■which 
  ])eshay(S 
  placed 
  in 
  his 
  group 
  of 
  " 
  Cncullaires, 
  ' 
  but 
  later 
  writers 
  (Conrad, 
  

   18(59, 
  Fischer, 
  and 
  others) 
  have 
  taken 
  his 
  first 
  species 
  (heterodonia) 
  of 
  that 
  group 
  as 
  

   the 
  type 
  of 
  the 
  genus 
  "Cucullaria," 
  which 
  differs 
  in 
  having 
  the 
  anterior 
  as 
  well 
  as 
  

   the 
  posterior 
  teeth 
  long 
  and 
  lamelliform 
  ; 
  hence 
  we 
  would 
  associate 
  Tertiary 
  species 
  

   like 
  Beniharca 
  adversidentata 
  with 
  the 
  livlug 
  deep-water 
  forms. 
  

  

  