ANTHRACOPTERA  AXD  AXTHRACOllYA. 
265 
Tol.  49.] 
Hill,  Burntisland,  Fife ;  Calder  Hall  and  Calder  Wood,  Inchkeith 
(Firth  of  Forth);  Wardie  Shales,  Water  of  Leith. 
Axthracomya  modiolaris.  (PI.  X.  figs.  24,  25,  and  26.) 
Unio  rnodiolaris ,  Sowerbv,  Trans.  Geol.  Soc.  ser.  2,  to1.  v.  pt.  3,  pi.  xxxix. 
fig.  10. 
Anthracomya  rnodiolaris,  Salter,  Mem.  Geol.  Surv.,  ‘  Iron  Ores  of  South 
Wales,’  pi.  ii.  fig.  13. 
Anthracomya  rnodiolaris,  Ward,  Trans.  North  Staffs.  Inst.  Min.  &  Mech. 
Eng.  voi,  x.  (1890)  pi.  i.  fig.  10. 
Specific  Characters. — Shell  inequilateral,  equivalve,  transversely 
elongated,  convex.  Dorsal  and  ventral  margins  subparallel,  hinge¬ 
line  straight,  somewhat  elevated  posteriorly.  Umbones  obtuse, 
adpressed,  situated  about  ^  distance  of  the  hinge-line  from  the 
anterior  end.  An  obtuse  oblique  ridge,  in  some  forms  sub- 
angular,  passes  obliquely  backwards  from  the  umbones  in  the 
direction  of  the  posterior-inferior  angle,  becoming  lost  on  the  sur¬ 
face  of  the  shell,  just  before  it  reaches  this  point.  Anterior  end 
short,  rounded,  much  compressed  below,  with  well-marked  diagonal 
sulcus,  anterior  to  the  ridge.  Posterior  end  flattened  rapidly  from 
the  oblique  ridge,  and  expanded  ;  the  posterior  end  is  truncate,  with 
rounded  superior  and  inferior  angles.  The  inferior  border  is  straight, 
and  gently  curved  where  it  passes  into  the  anterior  and  posterior 
borders. 
Interior. — Pallial  sinus  eutire.  Anterior-adductor  scar  elongate, 
at  the  junction  of  the  hinge-line  and  the  anterior  border.  Posterior- 
adductor  scar  large,  ovate,  near  the  posterior-superior  angle  of  the 
shell. 
Exterior. — Surface  marked  with  lines  and  strise  parallel  to  the 
lower  border,  becoming  curved  posteriorly,  very  slightly  so  anteriorly. 
Striae  more  dense  at  the  inferior  part  of  the  shell. 
Shell  thin.  Periostracum  strongly  wrinkled  in  some  specimens. 
Size. — Antero-posterior  measurement,  44  mm.  (l|inch);  dorso- 
ventral,  23  mm.  (^  inch) ;  from  side  to  side,  18  mm.  (j-i  inch). 
Remarks. — This  shell  somewhat  resembles  A.  dolabrata.  It 
occurs  at  an  entirely  different  horizon,  the  two  species  never 
appearing  together  in  Xorth  Staffordshire. 
Salter’s  figure  in  4  Iron  Ores  of  South  W7ales,’  pi.  ii.  fig.  13,  hardly 
agrees  with  Sowerby’s  shell,  but  has  all  the  appearance  of  a  small 
form  of  A.  Aclamsii.  The  comparative  measurements  and  shape 
are  very  similar ;  it  lacks  the  straight  lower  border,  the  more  acute 
form  of  the  diagonal  ridge,  and  besides  its  anterior  end  is  too  high, 
joining  the  inferior  border  with  too  great  a  curvature  to  belong  to  the 
species  under  description.  It  does  occur  in  the  South  Wales  Coal¬ 
field.  I  have  had  the  opportunity  of  examining  a  shell  from  the 
locality  in  the  collection  of  Mr.  J.  Ward. 
This  species  is  the  only  member  of  the  genus  which  has  been 
identified  from  a  Scottish  coalfield,  though  Mr.  B.  ‘Etheridge,  Jun., 
mentions  some  crushed  specimens  from  the  Bo'ness  Series ;  the  former 
is  confined  to  the  Middle  Coal  Measures. 
