55 
turellement  un  angle  à  leur  jonction.  Sa 
couleur  est  cornée  claire.  Les  tours  s’en¬ 
roulant  dans  un  même  plan,  le  centre  de  la 
spire  est  légèrement  et  également  enfoncé 
dessus  et  dessous.” 
The  author  of  the  name  received  the 
species  from  Bahia.  BAKER  observed  it  in 
the  lake  Papary  and  we  found  it  in  thecjty  of 
Parahyba  (Lagoa  de  Baixo),  principally  on 
the  roots  of  Pistia  stratiotes. 
The  animal  is  very  much  like  that 
of  melleus  LUTZ,  showing  the  same  yellow 
stripe  on  the  head,  while  the  black  pigment 
of  the  whole  skin  and  the  red  one  of  the 
blood  are  equally  wanting.  The  colour  of 
the  body  is  opaque,  ocraceous-white,  like  in 
many  species  of  Helix ,  with  the  inner  parts 
almost  transparent;  the  very  thin  shell  is  al¬ 
most  hyaline,  only  shightly  yeliowish. 
Plano rbis  citnex ,  melleus  and  cult r a  tus 
seem  to  belong  to  the  genus  Spirulina  to¬ 
gether  with  depressissimus  and  a  few  other 
small  and  flat  species.  In  those  I  found  no  pa¬ 
rasites,  nor  do  they  seem  to  be  concerned  in 
the  transmission  of  Schistoso/num. 
Î0.  Planorbis  cultratus  D’ORBIGNY 
(Plate  XVIII  fig,  10  a,  b,  c,  d). 
This  species  was  described  first  from 
Cuba  but  it  occurs  also  in  Martinique  and 
on  the  american  continent.  A  species,  thus 
determined  by  VON  MARTENS,  does  not 
seem  to  be  rare  in  Venezuela.  BAKER  found 
six  specimens  in  the  lake  of  Papary  near 
Natal  and  considered  this  as  the  most 
southern  habitat  observed.  VON  MARTENS, 
however,  mentioned  it  as  living  in  Paraguay, 
where  I  have  since  found  it  too.)  I  collected 
many  specimens  in  Lagoa  de  Carro  and 
some  in  Limoeiro  and  in  Victoria,  in  the 
State  of  Pernambuco,  while  Dr.  PENNA 
found  it  in  Pau  d’Alho.  It  is  easily  recog¬ 
nised  by  its  marked  characteristics,  which 
place  it  in  the  sub-genus  Spirulina  together 
with  citnex  and  melleus. 
Original  description  of  D’ORBIGNY: 
“ Planorbis  cultratus  D’ORB.,  Planorbe 
tranchant  Tab.  XIV,  fig.  5,  S. 
Planorbis  testâ  discoideâ,  depressissimâ, 
tenui,  diaphanâ,  laevigata,  succineâ,  superne 
concavâ,  subtus  complanatâ,  ad  peripheriatn 
carinato-cultratâ,  marginatâ,  anfractibus  sex 
angulatis,  supra  convexis,  subtus  complanatis. 
aperturâ  triangulan  depressâ. 
Dimensions,  Diamètre . 9  mîTlim 
Hauteur .  1  millim 
Coquille  discoidale  très  déprimeé,  mince, 
fragile,  transparente,  légèrement  concave  en 
dessus,  horizontale  en  dessous,  dont  le  pour¬ 
tour  est  fortement  caréné,  tranchant  et  mar¬ 
qué  d’une  bordure  linéaire.  Spire  composée 
de  6  tours  anguleux,  convexes  et  séparés 
par  des  sutures  marquées  en  dessus,  apla¬ 
ties  en  dessous. 
Bouche  triangulaire,  étroite,  transversale¬ 
ment  déprimée;  son  angle  est  aigu  et  évidé 
en  dessus. 
Couleur.  Succinée  ou  verdâtre. 
Autant  et  plus  déprimée  que  le  P.  com- 
pressus,  cette  espèce  est  bien  plus  triangu¬ 
laire,  plus  carénée  et  á  tours  de  spire  plu-s 
larges.  Parmi  les  espèces  américaines,  notre 
Planorbis  kermatoides  est  le  seul  qu’on 
puisse  lui  comparer;  néanmoins  le  P.  eultra- 
tus  s’en  distingue  par  sa  plus  grande  dépres¬ 
sion,  par  sa  carène  tranchante  et  bordée. 
Nous  en  devons  la  connaissance  à  M. 
de  Candé,  mais  nous  ne  la  plaçons  qu’avec 
doute  parmi  les  espèce*  de  Cuba,  craignant 
qu’elle  ne  soit  de  la  Martinique  plutôt  que 
de  Pile  espagnole”. 
(Histoire  physique,  politique  et  naturel¬ 
le  de  l’Ile  de  Cuba  par  M.  Ramon  de  la 
Sagra.  Mollusques  par  Alcide  d’Orbigny,  L, 
p.  196,  1835). 
In  Lagoa  de  Carro  I  found  cultratus 
sticking  to  a  drifting  piece  of  wood  or  floa¬ 
ting  horizontally  on  the  surface  of  a  large 
excavation,  which  had  been  made  in  a  brick- 
factory  and  was  filled  with  dirty  water  with¬ 
out  any  plants  ;  in  other  places  on  Pistia 
stratiotes  and  Polygonum  hydropiper.  The 
animal  has  the  same  colour  and  the  same 
orange-yellow  stripe  as  melleus  and  cultratus. 
The  shell  is  also  carried  horizontally. 
11.  Planorbis  (Spirulina)  nigellus  n.  sp. 
Colour  of  the  shell  the  same  as  in  melleus 
but  appearing  black  where  the  living  animal 
