Yol.  49.] 
ANTHRACOPTEEA  AND  ANTHRACOMYA. 
253' 
of  his  A.  funata  and  Modiola  subtruncata  are  much  better,  and  have 
every  appearance  of  the  shell  under  description.  They  are  both, 
moreover,  from  the  same  locality  (Wakefield). 
Anthracoptera  triangularis.  (PI.  VII.  figs.  7,  8,  9,  9  a.) 
Mytilus  triangularis,  Sowerby,  Trans.  Geol.  Soc.  ser.  2,  vol.  v.  pt.  3,  pi.  xxxix- 
fig.  16. 
?  Avicula  modioli  formis,  Brown,  ‘  Fossil  Conckology,’  pi.  lxvi.*  fig.  19. 
Myalinci  Swallovi,  McChesney,  ‘  New  Sp.  Palaeozoic  Foss.’  p.  57,  1860. 
,,  ,,  ,,  Illustrations  to  same,  pi.  ii.  figs.  6,  6  a. 
,,  ,,  Meek  &  Wortken,  ‘Geol.  of  Illinois,’  Pakeont.  vol.  ih 
(1866)  pi.  xxvii.  fig.  1  a,  b,  c,  d. 
Specific  Characters — Shell  much  compressed,  obliquely  ovate,  with 
pointed  anterior  end,  and  the  posterior  regularly  and  semieircularly 
curved  into  the  upper  and  lower  borders.  Hinge-line  straight,  about 
^  length  of  shell,  from  which  point  the  superior  border  slopes  gently 
downwards  into  the  curve  of  the  posterior  end.  Left  valve  most 
convex,  with  a  diagonal  ridge  proceeding  from  the  umbones,  which 
becomes  lost  when  it  has  traversed  ^  the  length  of  the  shell.  It  is 
not  twisted  as  in  previous  species.  Beaks  situated  at  h  length  from 
the  anterior  end  of  the  hinge-line,  only  slightly  curved  forwards. 
Anterior  end  small  and  tumid.  Inferior  border  nearly  straight.  The 
posterior  end,  produced,  slightly  expanded,  and  flattened,  comprises 
|  of  the  shell. 
Interior . — Three  pit-like,  anterior-adductor  muscle-scars  ;  one 
posterior,  position  uncertain. 
Surface-markings  as  in  previous  species. 
Greatest  length,  38  mm.  (1T7^  inch) ;  greatest  dorso-ventral 
depth,  21  mm.  (j-|  inch  ;  this  is  close  to  the  posterior  end) ;  thick¬ 
ness,  10  mm.  (§  inch). 
Remarks. — The  shells  form  a  group,  distinguished  from  A.  moclio- 
laris  by  a  comparatively  short  hinge-line,  and  flatter,  more  oblique 
form,  with  a  less-marked  diagonal  ridge,  which  has  not  the  obtuse 
change  in  direction  near  its  apex.  It  is  distinguished  from  A.  carinata 
by  its  more  expanded  and  produced  form,  and  less  tumid  and  keeled 
valves  ;  but  intermediate  forms  exist,  connecting  all  three  forms. 
Localities. — North  Staffordshire  :  roof  of  Hard  Mine  Coal  ; 
Coalbrookdale  :  Crawstone  ;  Woodhall,  Water  of  Leith  (Bhind). 
Anthracoptera  carinata.  (PL  VII.  figs.  2, 2  a,  10,  10  a,  11, 12, 12 a.) 
Modiolcl  carinata ,  Sowerby,  Trans.  Geol.  Soe.  ser.  2,  vol.  v.  pt.  3,  pi.  xxxix. 
fig.  15. 
Modiola  carinata,  Brown,  ‘  Fossil  Conckology,’  pi.  lxi.***  figs.  19,  20. 
Myalina  carinata ,  Salter,  Geol.  Surv.  Mem.,  ‘  Iron  Ores  of  Soutli  Wales/ 
pi.  ii.  fig.  15. 
j Dreissenia  dilatata,  Ludwig,  ‘  Pakcontograpkica,’  vol.  viii.  pi.  lxxi.  figs.  5,  6,  7. 
Anthracomya  carinata,  Hull,  ‘  Coalfields  of  Great  Britain,’  4tk  ed. 
pi.  facing  p.  38,  fig.  3. 
A.  carinata,  Ward,  Trans.  Nortk  Staffs.  Inst.  Min.  &  Meek.  Eng.  vol.  x, 
(1890)  p.  129,  pi.  i.  fig.  9. 
No  name,  B,.  Garner,  ‘  Nat.  Hist,  of  County  of  Stafford,’  pi.  E,  fig.  19. 
Specific  Characters. — Shell  obliquely  rhomboidal,  but  the  anterior 
lobe  is  larger  comparatively  than  in  the  two  foregoing  species.  An¬ 
terior  and  posterior  margins  almost  parallel ;  lower  margin  short  and 
