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MR.  BRODERIP  ON  THE  GENUS  CHAMA. 
points  it  agrees  with  Lamarck's  Chama  florida ;  but  he  describes  the  margin  of  that 
shell  as  entire,  whereas  the  margin  of  Chama  Pacifica  is  strongly  crenated. 
Mr.  Cuming's  specimens  were  obtained  by  diving.  They  were  attached  to  Avicula 
{MeleagrincB,  Lam.,  MargaritcB,  Leach,)  at  a  depth  ranging  from  three  to  seven 
fathoms. 
Many  shells  of  this  species  were  brought  to  this  country  some  years  ago,  from  the 
Pearl  Islands,  by  Mr.  Samuel  Stutchbury. 
Chama  imbricata. 
Tab.  XXXIX.  Fig.  2. 
Chama  testa  lamellosd,  squamis  imbricatd,  albidd  purpureo-fusco  varid ;  valvd  superiore 
subdepressd,  suhlobatd,  sinu  ab  umbone  usque  ad  limbum  currente  j  intus  albidd,  limbo 
integro  sapissime  nigro-purpureo. 
Hab.  in  Oceano  Pacifico.    (Lord  Hood's  Island,  Pearl  Islands.) 
This  grows  to  a  large  size,  and  was  obtained  by  diving  by  Mr.  Cuming,  attached  to 
Avicula  at  a  depth  ranging  from  three  to  seven  fathoms.  There  is  generally  a  purple 
spot  at  the  tip  of  the  umbo  of  the  upper  valve. 
This  also  was  brought  home  in  considerable  numbers  by  Mr.  Samuel  Stutchbury  from 
the  Pearl  Islands,  and  I  have  more  than  once  been  inclined  to  think  that  it  may  be  a 
variety  of  Chama  Pacifica.  But  the  internal  edge  of  the  former  is  always  crenated,  that 
of  the  latter,  except  towards  the  hinge-border,  is  smooth,  and  the  depressed  line  of  its 
upper  valve  is  very  strongly  marked,  however  the  external  shape  may  vary. 
Var.  a.  Nana,  castanea  albo  strigata,  intus  alba. 
Tab.  XXXIX.  Fig.  3. 
Hab.  ad  Insulas  Gallapagos  dictas. 
The  examination  of  an  extensive  series  has  led  me  to  the  conclusion  that  this  dwarf, 
and  at  first  sight  widely  differing,  shell,  is  only  a  variety  of  Chama  imbricata.  The  pur- 
ple brown  is  changed  into  chestnut  striped  with  white  ;  and  hardly  any  scales  are  to  be 
found  on  its  wrinkled  surface  except  the  double  series  which  crown  the  ridge  on  each 
side  of  the  depressed  line,  and  sometimes  a  series  or  two  on  the  affixed  valve.  This 
depressed  line  is  not  nearly  so  well  marked  as  it  is  in  the  large  variety,  but  it  is  to  be 
observed  on  most  of  the  specimens  :  some  are  absolutely  without  imbrications. 
A  figure  of  one  of  these  turning  from  right  to  left  (some  specimens  turn  from  left 
to  right)  is  given. 
This  variety  was  found  by  Mr.  Cuming  attached  to  rocks  and  stones  at  low  water. 
