266 
DE.  WHEELTON  HIND  ON  THE  AFFINITIES  OF  [May  I  893, 
Locality. — Hard  Mine  and  Ten-foot  Seams,  North  Staffordshire 
Coalfield  ;  Crawstone,  Coalbrookdale ;  Black  Mine,  Oldham  ;  ?  South 
"Wales  ;  Durham  Coalfield  ;  Scotland. 
Antheacomya  elongata.  (Pl.  X.  figs.  1-12.)  "Williamson  MSS. 
Modiola  WiUiamsoni,  Brown,  ‘  Fossil  Conchology,’  pl.  lxxi.  figs.  24,  25. 
Aon  Naiadites  (Antliracomya)  elongata,  Dawson,  ‘  Acadian  Geology,’  2nd  ed. 
(1868)  p.  204,  fig.  48. 
Specific  Characters. — Slightly  inequivalve,  the  left  being  the 
larger;  inequilateral;  transversely  elongate  ;  greatest  dorso-ventral 
measurement  at  the  posterior  end  of  the  shell.  Hinge-line  straight, 
edentulous,  raised  posteriorly.  Umbones  small,  contiguous,  situated 
at  rather  less  than  |  distance  of  the  hinge-line  from  the  anterior 
margin.  Inferior  border  nearly  straight,  slightly  sinuated  about  its 
centre.  Lunule  small  and  elongated.  Anterior  end  sharp,  com¬ 
pressed,  with  an  acutely  rounded  border  passing  rapidly  down¬ 
ward  into  the  inferior  border.  Posterior  end  expanded  and  very 
slightly  flattened,  except  above,  where  it  is  rapid!}7  compressed 
into  the  hinge-line,  its  posterior  border  being  truncate  with 
bluntly  rounded  angles ;  generally  gaping.  A  broad,  obtuse 
gibbosity  passes  from  the  umbones  diagonall}7  across  the  shell,  in 
the  direction  of  the  inferior-posterior  angle,  with  a  slight  oblique 
sulcus  anterior  to  it,  reaching  the  inferior  margin  about  its  centre. 
Cartilage  external.  Shell  small. 
Interior  nacreous  ;  pallial  sinus  entire,  with  lamellar  markings ; 
above  and  over  the  oblique  gibbosity  some  fine,  radiating  lines. 
Anterior-adductor  muscle-scar  situated  just  within  the  anterior 
border,  at  the  anterior-superior  angle  ;  large,  rounded  accessory  scar 
above,  and  nearer  the  umbo.  Posterior-adductor  scar  situated  just 
below  the  posterior  end  of  the  hinge-line,  large  and  rounded. 
Exterior. — Surface  covered  with  fine  concentric  lines,  which  be¬ 
come  parallel  to  the  inferior  border  as  they  pass  across  the  shell. 
Shell  very  thin. 
Size. — Antero-posterior  measurement,  35  mm.  (1|  inch);  dorso- 
ventral,  near  posterior  end,  17  mm.  (j-J  inch)  ;  greatest  lateral 
measurement  at  the  centre  of  the  shell,  5  mm.  (1  inch). 
Kernarlcs. — This  pretty  little  shell  is  very  variable,  scarcely  two 
specimens  being  exactly  alike.  Its  chief  variations  are  in  the 
position  of  the  umbones,  length  of  the  anterior  end,  comparative 
length  of  the  shell,  and  shape  of  the  posterior  end,  which  may 
be  bluntly  rounded  and  much  compressed.  I  find  in  Brown's 
‘Fossil  Conchology  5  a  figure  which  agrees  closely  with  mine,  to 
which  that  author  has  given  the  name  of  Modiola  WiUiamsoni 
at  the  same  time  referring  it  to  M.  elongata ,  MSS.  Williamson. 
I  adopted  the  latter  specific  name  as  having  the  right  of  prioritv, 
and  with  the  greater  pleasure  because  it  does  away  with  a 
meaningless,  purely  complimentary,  barbarous  term. 
Locality. — Hard  Mine  roof,  North  Staffordshire  Coalfield  (where 
it  is  fairly  common).  Most  museums  in  the  country  possess  these 
shells  from  this  bed. 
