ANTHRACOPTERA  AXD  AXTHRACOMYA. 
259 
Yol.  49.] 
ornamentation  of  some  recent  Siamese  Chios,  and  is  therefore  in  no 
way  peculiar  to  the  burrowing  Myacidee. 
There  is  no  evidence  at  all  that  these  shells  were  burrowers ;  in¬ 
deed  I  believe,  from  the  fact  that  they  are  always  associated  with 
byssiferous  Anthracoplera  and  other  members  of  the  Unionidae,  that 
they  were  not  so.  They  are  never  found  lying  at  right  angles  to 
the  lines  of  stratification  in  Korth  Staffordshire,  but  always  hori¬ 
zontal.  The  simple  edentulous  hinge-line,  external  ligament  (I  can 
find  no  evidence  of  an  internal  one  in  casts),  the  absence  of  pallial 
sinus,  position  and  shape  of  the  adductor-muscles  (though  the 
accessory  scars  posterior  to  the  anterior  adductor  appear  to  be 
absent,  as  Prof.  King  pointed  out  to  be  the  case  in  Anthracosia )  all 
are  characteristic  of  the  family  Unionidie. 
The  shells  approximate  closely  to  Anodon,  under  which  name 
Ludwig  has  described  several  Continental  forms,  but  they  lack  the 
eroded  obsolete  beaks,  the  supplementary  anterior-adductor  muscle- 
scar,  and  the  equal  valves  of  this  form.  Prom  Anthracosia  (King) 
they  differ  in  the  expanded  shape  of  the  posterior  end,  the  small  incon¬ 
spicuous  beaks,  and  the  absence  of  a  peculiar  hinge-plate  and  teeth. 
D’Orbigny  quotes  a  byssiferous  form  of  Anodon  as  found  in  the 
river  Parana,  South  America.  Most  forms  of  the  genus  have  traces 
of  a  byssal  sinus,  although  they  have  no  longer  a  byssus.  The 
sinuation  of  the  inferior  border,  the  obliquity  of  the  valves,  and 
the  absence  of  a  byssal  notch  in  Anthracomga  induce  one  to  suppose 
that  its  ancestors  or  embryos  may  have  been  byssiferous. 
Salter  firmly  believed  that  the  beds  in  which  Anthracosia ,  Anihra- 
comya,  and  Anthracoptera  w7ere  found  were  of  marine  or  highly 
brackish-water  origin,  his  view  being  formed  by  the  supposed 
affinities  of  the  latter  two  genera.  He  also  quotes  Agassiz  and 
De  Koninck  as  authorities  for  the  marine  character  of  Anthracosia ; 
but  it  must  be  remembered  that  both  these  observers  confused  the 
shells  with  Cardinia ,  a  typical  marine  genus,  and  their  view  has 
not  been  accepted  by  subsequent  writers  on  the  subject. 
There  are,  fortunately,  very  typical  marine  beds  of  various  depths 
in  the  Coal  Measures,  which  contain  an  unimpeachable  marine 
fauna,  e.  g.  Productus ,  Spirifer ,  Lingula ,  Discina ,  Orthoceras, 
Goniatites ,  Nautilus ,  Aviculopecten,  Posidonia ,  Edmondia ,  Sangui- 
nolites ,  etc.,  not  only  at  the  base  in  the  Gannister  Beds,  but,  as  occurs 
in  North  Staffordshire,  much  higher  up  in  the  Coal  Measures 
proper.  In  none  of  such  beds  do  Anthracosia ,  Anthracomya ,  and 
Anthracoptera  occur  ;  but,  on  the  other  hand,  these  genera  are  found 
associated  with  a  peculiar  fauna  of  fishes  and  reptiles,  annelids 
and  crustaceans,  which  have  a  close  affinity  with  recent  forms  and 
inhabit  fresh  water,  together  with  a  flora  of  ferns,  Sigillaria , 
Cala mites ,  and  Lepidodenclron. 
The  fact  of  typical  marine  fossils  being  found  in  a  few  beds  of 
small  extent,  intercalated  in  the  coal  strata,  seems  to  me  to  afford 
strong  evidence  that  the  rest  of  the  beds  were  not  of  marine  origin  ; 
it  would  indeed  be  unaccountable,  if  all  the  beds  were  marine, 
that  the  typical  fossils  should  not  be  more  generally  distributed- 
