[   21  ] 
IV.  On  the  Structure  and  Characters  of  Loligopsis,  and  Account  of  a  New  Species  (Lol. 
guttata,  Grant)  from  the  Indian  Seas.  By  Robert  E.  Grant,  M.D.,  F.R.S.  Ed., 
L.S.,  G.8.,  Z.S.,  Sfc,  Professor  of  Comparative  Anatomy  and  Zoology  in  the  University 
of  London. 
Communicated  February  12,  and  July  23,  1833. 
No  specimen  of  the  Loligopsis  of  Lamarck  appears  to  have  been  hitherto  brought  to 
Europe,  and  few  naturaUsts  are  at  present  wiUing  to  admit  the  existence  of  this  genus. 
Cuvier  only  mentions  it  in  his  '  Regne  Animal'  (torn.  iii.  p.  14.)  as  a  genus  founded  on 
drawings,  which  he  considered  of  Httle  authenticity,  and  makes  no  allusion  to  it  in  his 
Memoirs  on  the  Anatomy  of  the  Mollusca.  M.  Blainville  (Malacologie,  p.  367.  note) 
rejects  the  genera  Loligopsis  of  Lamarck  and  Leachia  of  M.  Le  Sueur,  from  their  being 
founded  on  imperfect  observations  and  figures,  and  from  their  affecting  to  present  on 
the  same  animals  the  caudal  fin  of  a  Loligo  along  with  only  eight  arms  around  the  head, 
as  in  the  Octopus.  He  regards  such  a  combination  of  characters  on  the  same  individual 
as  very  doubtful.  M.  Ferussac  is  of  opinion  that  in  the  present  uncertainty  of  naturalists 
regarding  the  Loligopsis,  the  species  might  be  referred  to  the  genus  Cranchia,  which  is 
a  Decapod  with  caudal  fins.  Lamarck,  however,  founded  his  genus  Loligopsis  on  a 
drawing  of  a  Cephalopod  observed  by  Peron  and  Le  Sueur  in  the  South  Sea,  which  had 
only  eight  equal  arms  around  the  head  along  with  the  caudal  appendices  of  a  Loligo ; 
that  species  he  denominated  Lol.  Peronii  (An.  s.  Vert.,  tom.  vii,  p.  659.).  M.  Le  Sueur 
has  founded  a  new  genus  Leachia  on  a  drawing  made  by  M.  Petit  from  a  similar  Octopod 
with  caudal  appendices,  obtained  from  the  South  Pacific  (Journ.  of  the  Acad,  of  Nat. 
Sci.  of  Philadelphia,  vol.  ii.  Part  L  p.  90.).  As  the  Loligopsis  of  Lamarck,  and  the 
Leachia  of  M.  Le  Sueur,  differ  only  in  the  length  of  the  arms,  M.  Rang  (Hist,  des  Mol- 
lusques,  p.  87.)  has  very  properly  rejected  this  generic  distinction,  and  regarded  the 
two  terms  as  synonyms  ;  the  Leachia  cyclura  of  M.  Le  Sueur  forms  therefore  a  second 
species  of  Loligopsis  in  M.  Rang's  use  of  the  term,  and  the  species  I  have  now  to  describe 
forms  a  third  of  the  same  genus. 
All  the  Naked  Cephalopods  are  Octopods,  the  disk  which  produces  these  feet  by  its 
division  never  producing  a  greater  number  than  eight ;  but  in  many  genera  two  re- 
tractile pedunculated  tentacula  are  developed,  and  extend  from  within  this  outer  sub- 
divided disk,  and  generally  between  the  first  and  second  anterior  arms  on  each  side, 
which  has  given  rise  to  the  division  termed  Decapoda  in  this  class.  The  tentacula, 
however,  never  assume  the  form  of  the  other  feet.  The  peculiarity  of  the  Loligopsis 
is  therefore  not  the  want  of  any  of  the  usual  eight  feet,  but  the  want  or  imperfect  de- 
