ANTHRACOPTERA  AXD  AXTHRACOMYA. 
Tol.  49.] 
267 
Anthracomya  laxceolata,  sp.  nov.,  Wheelton  Hind.  (PI.  X.  figs.  13, 
13  a.) 
Modiola  lithodomoides.  R.  Etheridge.  Jun.,  &  J.  Ward,  Trans.  North  Staffs. 
Inst.  Min.  &  Mech.  Eng.  vol.  x.  (1890)  p.  130,  pi.  i.  fig.  11. 
Specific  Characters. — Shell  slightly  ineqnivalve,  much  elongated 
transversely,  with  rounded  ends.  Hinge-line  straight,  about  £ 
length  of  the  shell,  not  raised  posteriorly.  Umbones  small,  only  just 
raised  above  the  hinge-line,  obtuse,  not  contiguous,  situated  T 
length  of  the  shell  from  the  anterior  end.  Lunule  narrow  and 
elongated.  Anterior  end  much  lower  than  the  umbones,  short, 
almost  straight  above,  rounded  below,  convex.  The  posterior  end 
is  elongated,  flattened,  lanceolate,  only  slightly  expanded  below. 
There  is  a  slight  oblique  sulcus  which  indents  the  inferior  border, 
at  the  junction  of  the  anterior  with  the  middle  third  of  the  shell. 
The  shell  is  moderately  convex  in  its  anterior  two-thirds,  being 
gradually  flattened  above,  below,  and  posteriorly  in  the  hinder 
third.  Inferior  border  straight  for  ^  its  length,  then  slightly 
sinuated,  and  then  produced  downward  in  a  straight  line  at  a  slight 
angle,  till  it  curves  bluntly  upward  to  meet  the  posterior  border. 
Interior  smooth  ;  anterior-adductor  muscle  large,  just  within  the 
anterior-superior  angle  of  the  shell.  Posterior  unknown.  Shell 
thin,  ligament  external. 
Exterior. — Surface  covered  with  fine  lines  and  laminae  of  growth. 
Size. — Antero-posterior  measurement,  32  mm.  (1|  inch)  ;  greatest 
dorso-ventral,  ^  from  posterior  end,  10  mm.  (J-  inch) ;  from  side  to 
side,  centre  of  shell,  7  mm.  (yy  inch). 
Remarks. — I  know  of  only  two  examples  of  this  species,  which  is 
separated  from  other  species  by  the  absence  of  a  raised  hinge-line 
posteriorly,  and  by  the  acute  and  generally  flattened  posterior  end. 
It  has  no  similarity  to  Modiola  lithodomoides ,  it.  Etheridge,  Jun., 
Geol.  Mag.  for  1875,  p.  211,  a  Mountain  Limestone  species  much 
larger  than  our  specimen.  One  was  picked  up  at  the  Glebe  Colliery, 
Fenton  ;  exact  horizon  unknown. 
Locality. — Bowling  Alley  Seam,  Middle  Coal  Measures,  "Whitfield 
Colliery,  North  Staffordshire. 
Axthracomva  obtusa.  (PI.  X.  figs.  11,  11  a .) 
Unio  obtusus,  Ludwig,  ‘  PaHontographica,’  vol.  viii.  pi.  iv.  fig^.  13-15. 
Ileurophorus  subcost afus,  Meek  &  Wortben,  ‘  Geol.  of  Illinois,’  Palajont., 
vol.  ii.  (1866)  pi.  xxvii.  figs.  2,  2  a. 
Specific  Characters. — Shell  very  inequilateral,  oblong.  Anterior 
end  very  bluntly,  obtusely  rounded.  Posterior  end  truncate  ;  the 
superior  and  inferior  angles  rounded;  the  superior  and  inferior  borders 
nearly  parallel.  Hinge-line  curved  anteriorly  as  far  as  the  umbo, 
afterwards  straight  and  slightly  elevated,  edentulous.  Fmbones 
almost  anterior,  otherwise  separate,  about  as  high  as  the  hinge-line. 
Lunule  well  marked.  Inferior  border  very  slightly  sinuated.  An¬ 
terior  end  almost  obsolete,  moderately  convex ;  posterior  elongated, 
gently  flattened,  compressed  above  into  the  hinge-line.  An  almost 
