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MR.  J.  O.  WESTWOOD  ON  NYCTERIBIA. 
furnished  with  strong  bristles  ;  they  are  all  similarly  formed,  and  of  a  similar  size  ;  and 
the  sexes  appear  to  offer  no  variation  in  respect  to  their  structure.  They  are  inserted, 
as  above  stated,  at  the  anterior  and  lateral  margins  of  the  thorax,  the  pectoral  shield 
extending  beneath  their  bases,  so  that  their  motions  have  necessarily  an  upward  direc- 
tion. In  the  anterior  pair  the  cox(b  are  distinct,  bristly,  and  somewhat  elongated.  I 
cannot,  however,  perceive  in  Colonel  Sykes's  species  the  coronet  of  bristles  noticed  by 
M.  Dufour  as  being  placed  at  the  extremity  of  the  "  premier  article  de  leur  hanche;"  but 
this  part  in  the  two  hinder  pairs  is  soldered  to  the  sides  of  the  thorax.  The  trochanter 
is  very  short ;  the  femora  are  thickened  and  compressed,  having  a  transverse  im- 
pression before  the  middle  of  the  limb,  as  indicating  a  rudimental  articulation.  The 
tihi(B  are  more  slender,  but  not  longer,  than  the /emora,  having  three  rudimental  articu- 
lations towards  the  base,  and  not  being  furnished  with  spurs  at  the  tips.  The  basal  joint 
of  the  tarsi  is  very  long,  and  appears  to  be  annulated.  The  three  following  joints  are  very 
short,  whilst  the  terminal  one  is  much  larger,  and  furnished  with  a  pair  of  large  pulvilli 
and  two  strong  curved  claws,  dilated  at  the  base  beneath ;  a  small  portion  of  the  base 
of  each  claw  being  less  crustaceous,  and  differently  coloured  from  the  remainder. 
Dr.  Leach,  regarding  the  coxcb  as  portions  of  the  femora,  and  overlooking  the  tro- 
chanter, described  the  femora  as  composed  of  two  joints.  In  like  manner  he  regarded 
the  long  basal  joint  of  the  tarsi  as  a  portion  of  the  tihia,  which  he  also  described  as  two- 
jointed,  while  he  considered  the  terminal  joint  of  the  tarsi  as  forming  two  joints,  evi- 
dently regarding  the  differently-coloured  base  of  the  ungues  as  a  distinct  articulation. 
The  structure  of  the  abdomen  and  its  appendages  varies  considerably  in  the  sexes  of 
Nycterihia  as  well  as  in  the  different  species.  This  circumstance,  united  to  the  uncer- 
tainty as  to  the  determination  of  the  individuals  of  each  sex,  has  been  the  source  of 
great  confusion  in  almost  every  description  hitherto  given  of  the  genus.  This  con- 
fusion I  am  enabled,  by  the  assistance  of  Colonel  Sykes's  specimens,  to  clear  up.  I 
have  said  that  these  specimens  were  females  in  various  stages  of  gestation.  In  none 
were  traces  of  articulation  visible  on  the  upper  surface  except  a  single  one  at  the  base, 
which,  on  the  under  side,  is  very  conspicuous,  being  flattened,  horny,  and  of  the  same 
colour  as  the  under  side  of  the  thorax,  while  the  rest  of  the  abdomen  is  coriaceous  and 
of  a  dirty  whitish  colour.  This  segment  is  terminated  by  a  transverse  series  of  very 
strong  and  blunt  black  bristles,  which  exist  in  all  the  individuals  of  the  genus  which  I 
have  examined.  By  Dr.  Leach  and  Mr.  Curtis  it  was  regarded  as  the  postpectus  ;  but 
that  it  is  a  portion  of  the  abdomen  is  evident  by  its  terminal  series  of  bristles  being  con- 
tinued laterally  and  extending  a  short  distance  across  the  upper  surface  of  the  base  of 
the  abdomen,  as  represented  in  my  figures :  indeed,  sometimes,  according  to  Latreille, 
it  is  entirely  continuous,  both  on  the  upper  and  lower  surface,  at  the  extremity  of  this 
basal  articulation. 
The  abdomen  itself  is  of  an  oval  form  and  very  convex  when  distended,  being  slightly 
