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DR.  WHEELTON  HIND  ON  THE  AFFINITIES  OF 
[May  1893, 
its  margin  slightly  sigmoidal.  Hinge-line  straight,  as  long  as 
the  shell,  its  margin  thickened  on  each  valve,  leaving  in  casts  two 
long  grooves.  Umbones  well  developed,  contiguous,  hut  not  touching, 
anterior,  hut  not  quite  terminal,  with  a  broad,  very  obtusely  rounded, 
diagonal  ridge  proceeding  from  each,  to  which  the  shell  owes  much 
of'  its  exceedingly  convex  form.  Byssal  furrows  shallow,  most  pro¬ 
nounced  in  the  left  valve ;  marginal  notch  not  deeply  excavated. 
Anterior  muscular  impressions  quite  anterior,  infra-umbonal.  Sur¬ 
face  of  the  shell  covered  with  concentric  subimbricating  lamellse. 
crowded  and  striiform  on  the  anterior  end,  hut  opening  out  and 
becoming  lamellar  on  the  diagonal  ridge  and  posterior  wing.” 
“  Obs. — The  much  more  central  position  of  the  diagonal  ridge, 
greater  convexity  of  the  shell,  and  the  sigmoidal  margin  of  the  pos¬ 
terior  end  at  once  distinguish  A.  obesa  from  either  Anthracoptera  ? 
or  Mycilina  (. Avicula )  quadrat  a,  Sow.,  A.?  or  M.  (. Avicula )  modiolaris, 
Sow.,  A.  ?  or  My.  ( Modiola )  carinata ,  Sow.” 
I  personally  know  nothing  of  this  form,  and  have  copied  word  for 
word  Mr.  E.  Etheridge's  description  and  remarks. 
Anthracoptera  elongata,  sp.  nov.,  Wheelton  Hind.  (PI.  YII. 
figs.  15,  15  a,  16,  17.) 
Specific  Characters. — Shell  inequivalve,  very  inequilateral,  modio- 
liform,  or  transversely  elongated,  tumid.  Hinge-line  straight,  about 
I  the  length  of  the  shell.  Peaks  almost  terminal,  separated,  directed 
forwards.  A  very  tumid  ridge  extends  from  the  umbones  diagonally 
across  the  shell  to  the  posterior  inferior  angle.  Anterior  end  almost 
obsolete,  swollen,  with  wide  byssal  sulcus.  Posterior  end  tumid 
below,  flattened  upwards  and  backwards,  and  somewhat  expanded. 
Posterior  border  bluntly  curved  above,  truncate  below.  The  in¬ 
ferior  border  would,  if  produced  forwards,  make  an  acute  angle  with 
the  hinge-line,  is  broadly  sinuated,  and  notched  for  the  bvssus. 
Interior.  All  that  is  known  is  that  there  is  a  very  large  anterior- 
adductor  muscle  and  another  pit-like  scar  in  the  umbo. 
Exterior. — -  Surfaces  marked  with  fine  stria?  and  lines  of  growth 
anteriorly,  which  diverge  slightly  until  they  reach  the  oblique 
ridge,  where  they  become  rapidly  reflected  upwards  and  pass  to  the 
superior  border. 
Size. — Greatest  antero-posterior  measurement,  23  mm.  (J-|  inch) ; 
greatest  dorso- ventral  measurement,  ^  from  posterior  end,h8  mm. 
(-i^-  inch)  ;  from  side  to  side,  5  mm.  (T  inch). 
Remarks.— This  is  a  rare  species,  limited,  so  far  as  I  know,  to  the 
Knowles  Ironstone  01  Fenton  and  Eongton.  It  can  be  distinguished 
from  all  other  species  by  its  tumid,  elongated,  subparallel  form. 
There  is  a  block  of  Knowles  Ironstone  in  the  Museum  of  Practical 
Geology,  Jerrnyn  Street,  which  contains  a  large  number  of  these 
shells.  The  younger  forms  are  more  oblique  and  less  tumid.  This 
species  very  closely  resembles  some  species  of  Anihracomya  ;  hut  the 
distinctive  features  of  the  umbonal  region  serve  to  point  out  the 
differences. 
Locality. — Knowles  Ironstone,  Fenton  Park,  Korth  Staffs. 
