270  DR.  WHEELTON  HIND  ON  THE  AFFINITIES  OF  [May  1 893, 
Anthracomya  senex.  (PI.  X.  figs.  20,  20  a,  and  21.) 
Salter,  Geol.  Surv.  Mem.,  ‘Iron  Ores  of  South  Wales,’  pi.  ii.  fig.  12, 
p.  231. 
Specific  Characters. — They  are  thus  described  by  Salter : — 
“  One  inch  wide  (antero-post.),  very  unequal-sided  (modioliform),  the 
beaks  close  to  the  anterior  end,  which  is  divided  by  a  well-marked 
byssal  furrow  and  notch  from  the  posterior  side  ;  the  latter  is  convex 
along  the  blunt  siphonal  ridge.  Anterior  side  very  short,  its  edge 
falling  vertically  under  the  rather  prominent  beak.  The  posterior 
side  (or  slope)  is  expanded  and  very  convex ;  the  hinge-line  raised  ; 
the  ventral  margin  sinuate  and  concave. 
“  Epidermis  deeply  wrinkled  V-fashion  over  the  posterior  slope/’ 
llemarks . — The  type-specimen  is  in  the  Museum  of  Practical 
Geology,  Jermyn  Street.  I  have  obtained  and  T  figure  here  specimens 
of  this  form  from  the  Hard  Mine  Seam,  Longton,  Xorth  Stafford¬ 
shire. 
Anthracomya  oboyata,  sp.  nov.,  Wheelton  Hind.  (PI.  X.  figs.  22 
and  22  a.) 
Specific  Characters. — Shell  obovate,  inequivalve,  the  left  valve 
being  more  convex.  Anterior  end  almost  obsolete,  tumid,  bluntly 
pointed.  Posterior  end  expanded,  flattened  backward  and  down¬ 
ward  and  into  the  hinge-line,  which  is  much  raised.  The  hinge¬ 
line  is  straight,  about  f  length  of  the  shell.  Umbones  prominent, 
blunt,  separate,  situated  |  distance  of  the  hinge-line  from  the 
anterior  end.  The  inferior  border  is  curved  rapidly  downward 
from  the  anterior  end,  then  becomes  bluntly  and  gently  rounded 
into  the  posterior  border,  which  extends  in  the  form  of  a  regular 
semicircular  curve  from  the  inferior  to  the  superior  angle.  A 
blunt  swelling,  rapidly  flattened  on  its  posterior  side,  extends  from 
the  umbo  to  a  point  in  the  inferior  border,  anterior  to  its  posterior 
limit.  There  is  no  appreciable  byssal  sulcus,  but  there  appears  to 
have  been  a  byssal  notch  at  the  junction  of  the  anterior  and  middle 
thirds  of  the  inferior  border. 
Interior  smooth,  with  folds  of  growth ;  anterior-  and  posterior- 
adductor  scars  as  in  other  species.  Ligament  external.  Lunule 
distinct. 
Size. — Antero-posterior  measurement,  30  mm.  (IP  inch)  ;  greatest 
dorso-ventral  (at  posterior  end),  17  mm.  (^  inch)  ;  from  side  to 
side,  7  mm.  (j5^  inch). 
Remarks. — I  have  found  only  one  specimen  of  this  very  distinct  and 
characteristic  form.  It  looks  much  like  some  forms  of  Anthracoptera, 
from  which  it  can  be  distinguished  by  its  umbones  and  hinge-line. 
It  has  occurred  to  me  that  this  may  well  be  an  example  of  mimicry, 
the  more  so  because  the  new  form  Anthracoptera  elongata  resembles 
very  closely  certain  forms  of  Anthracomya  (see  p.  256)  ;  in  fact,  it  is 
only  on  very  close  examination  of  the  umbones  and  binge-lines  that 
these  forms  can  be  correctly  referred  to  their  proper  genera.  This 
shell  closely  resembles  Naiadites  (. A  nthracomya )  carbonaria ,  Dawson, 
