MR.  J.  O.  WESTWOOD  ON  NYCTERIBIA. 
277 
served  in  spirit;  to  J.  F.  Royle,  Esq.,  who  has  permitted  me  to  examine  a  smaller 
Indian  species  collected  by  himself;  and  to  J.  F.  Stephens,  Esq.,  who  has  granted  to 
me  the  loan  of  his  specimens  of  Nijct.  Hermanni  and  Nyct.  Latreillii,  which  he  obtained 
from  Dr.  Leach  himself.  I  have  likewise  examined  Dr.  Leach's  three  specimens  of  his 
Nyct.  Latreillii,  three  of  his  Nyct.  Hermanni,  a  specimen  apparently  of  the  latter  species 
received  by  him  from  Bonelli,  and  the  original  specimen  of  his  Nyct.  Blainvillii,  all  con- 
tained in  the  cabinets  of  the  British  Museum. 
As  Colonel  Sykes's  specimens  have  afforded  the  clue  to  the  determination  of  the 
sexes,  in  consequence  of  their  being  in  different  stages  of  gestation,  and  as  they  are 
of  a  large  size,  and  moreover  preserved  in  spirit,  thus  affording  the  means  of  a  more 
satisfactory  examination,  I  propose,  in  the  first  place,  to  notice  their  structure  in  detail, 
comparing  it  with  that  of  the  already  described  species,  and  endeavouring  to  clear  up 
the  various  difficulties  existing  in  the  works  of  previous  observers ;  in  the  second,  to 
describe  more  concisely  the  structure  of  the  other  species  which  I  have  myself  examined  ; 
and  in  the  third  place  to  attempt  a  synopsis  of  the  various  species. 
The  three  individuals  of  Colonel  Sykes's  East  Indian  species,  which  I  have  inscribed 
with  his  name,  vary  somewhat  in  size,  according  to  the  degree  of  gestation,  from 
2  to  2-L  lines  in  length,  and  about  7  lines  between  the  extremities  of  the  anterior  and 
posterior  legs  when  stretched  out. 
The  body  is  of  a  crustaceous  texture,  with  the  exception  of  the  abdomen  and  upper 
teguments  of  the  thorax,  which  are  of  a  leathery  nature. 
The  head  (contrary  to  the  character  given  of  the  family  by  Dr.  Leach,  "  Head  united 
with  the  thorax,")  is  a  very  distinct  part  of  the  body,  although  when  at  rest  it  is  thrown 
backwards,  its  upper  surface  being  brought  into  contact  with  the  dorsal  membrane,  and 
its  under  surface  consequently  being  upwards.  It  is  affixed  to  the  anterior  part  of  the 
dorsum,  a  short  distance  behind  its  front  margin,  by  means  of  a  leathery  attachment, 
which,  when  dried,  assumes  the  appearance  of  a  distinct  neck,  thus  enabling  us  to  ac- 
count for  Latreille's  statement  of  the  head  of  his  misnamed  Nyct.  Blainvillii  being 
"  emplante,  au  moyen  d'un  article  tres  court,  servant  de  pedicule,  sur  le  dos  du  thorax;" 
by  this  means  the  head  is  not  only  raised  perpendicularly,  but  is  also  advanced  in  front 
until  it  assumes  a  horizontal  direction.  The  head  itself  is  small,  and,  as  Latreille  has 
well  described  it,  in  the  form  of  a  reversed  cone ;  but  it  is  crustaceous,  and  not  coria- 
ceous. M.  Dufour  states  that  its  place  of  insertion  is  "  dans  I'echancrure  anterieure 
du  corselet  justement  entre  les  hanches  des  pattes  de  devant ;"  but  in  no  individual 
which  I  have  examined  is  the  anterior  margin  of  the  thorax  at  all  emarginate,  being  on 
the  contrary  quite  rounded,  and  the  head  affixed  behind  rather  than  between  the  fore 
legs.  The  anterior  superior  margin  of  the  head  is  shghtly  emarginate,  but  much  more 
deeply  on  the  under  side,  where  the  large  base  of  the  central  apparatus  of  the  mouth 
is  attached.  The  upper  margin  (forming  the  base  of  the  reversed  cone)  is  furnished 
with  setae,  the  remainder  of  the  head  being  smooth  and  depressed. 
2  o  2 
