﻿Gatly 
  Marine 
  Lahoratory 
  , 
  St. 
  Andrews. 
  81 
  

  

  in 
  connection 
  with 
  the 
  proboscis, 
  which 
  forms 
  a 
  compara- 
  

   tively 
  hirge 
  and 
  thiciv-walled 
  organ 
  with 
  a 
  foliate 
  arrauge- 
  

   meut 
  of 
  its 
  mucous 
  lining 
  ; 
  au 
  external 
  coat 
  of 
  longitudinal 
  

   and 
  au 
  internal 
  layer 
  of 
  circular 
  muscular 
  fibres, 
  besides 
  the 
  

   external 
  sheath, 
  are 
  present, 
  The 
  mid-dorsal 
  and 
  mid-ventral 
  

   vascular 
  trunks 
  are 
  large, 
  the 
  latter 
  lying 
  between 
  the 
  ventral 
  

   ends 
  of 
  the 
  strong 
  oblique 
  muscles, 
  which 
  are 
  inserted 
  over 
  

   the 
  neural 
  canals, 
  which 
  are 
  large 
  and 
  situated 
  at 
  the 
  upper 
  

   border 
  of 
  the 
  nerve-area, 
  the 
  rest 
  of 
  the 
  area 
  being 
  hypo- 
  

   dermic. 
  

  

  The 
  first 
  foot 
  in 
  a 
  Canadian 
  example 
  (PI. 
  VI. 
  fig. 
  2) 
  is 
  

   minute 
  and 
  consists 
  of 
  a 
  fan-shaped 
  dorsal 
  lamella 
  and 
  a 
  

   smaller 
  ventral 
  one 
  of 
  ovoid 
  outline, 
  one 
  side 
  forming 
  the 
  

   adherent 
  base. 
  In 
  front 
  of 
  the 
  dorsal 
  lamella 
  is 
  a 
  group 
  of 
  

   strong 
  tapering 
  bristles, 
  with 
  a 
  basal 
  curvature 
  and 
  a 
  very 
  

   finely 
  tapered 
  tip, 
  the 
  centre 
  of 
  each 
  being 
  minutely 
  granular, 
  

   whilst 
  the 
  slender 
  tip 
  is 
  homogeneous. 
  The 
  ventral 
  tuft 
  is 
  

   composed 
  of 
  bristles 
  almost 
  straight, 
  but 
  having 
  as 
  finely 
  

   tapered 
  tips. 
  No 
  wings 
  could 
  be 
  defined 
  in 
  the 
  bristles 
  of 
  

   this 
  foot, 
  and 
  the 
  tufts 
  were 
  nearly 
  equal 
  in 
  size. 
  

  

  In 
  the 
  second 
  foot 
  of 
  the 
  ('anadian 
  form 
  (PI. 
  VI. 
  fig. 
  8) 
  

   the 
  dorsal 
  lamella 
  has 
  become 
  broadly 
  lanceolate, 
  its 
  lower 
  

   border 
  being 
  bluntly 
  round, 
  the 
  upper 
  somewhat 
  pointed. 
  

   The 
  ventral 
  lobe 
  is 
  elongate-ovoid, 
  with 
  the 
  I'ree 
  end 
  [)ointing 
  

   downward. 
  The 
  curvature 
  of 
  the 
  dorsal 
  bristles 
  is 
  less 
  

   marked, 
  the 
  centre 
  of 
  the 
  shaft 
  is 
  less 
  distinctly 
  granular, 
  and 
  

   there 
  is 
  a 
  barely 
  visible 
  trace 
  of 
  a 
  wing. 
  The 
  ventral 
  bristles, 
  

   on 
  the 
  other 
  hand, 
  are 
  more 
  evidently 
  curved, 
  are 
  larger, 
  and 
  

   of 
  two 
  kinds 
  — 
  longer, 
  curved, 
  finely 
  tapered 
  forms, 
  with 
  

   minute 
  grannies 
  in 
  the 
  shaft, 
  and 
  a 
  finely 
  tapered 
  tip, 
  

   Avithout 
  wings 
  ; 
  and 
  shorter 
  bristles, 
  with 
  translucent 
  shafts, 
  

   narrow 
  wings, 
  and 
  finely 
  tapered 
  tips. 
  

  

  The 
  third 
  foot 
  of 
  the 
  Canadian 
  form 
  has 
  a 
  considerably 
  

   larger 
  dorsal 
  lamella, 
  and 
  has 
  the 
  pinnate 
  process 
  in 
  front, 
  

   but 
  it 
  carries 
  no 
  branchia. 
  The 
  next 
  two 
  feet 
  (fourth 
  and 
  

   fifth), 
  however, 
  bear 
  well-developed 
  branchite 
  (Pi. 
  VI. 
  fig. 
  4), 
  

   that 
  following 
  (sixth) 
  having 
  a 
  conspicuous 
  dorsal 
  lamella 
  

   and 
  a 
  pinnate 
  process 
  on 
  each 
  side. 
  In 
  the 
  succeeding 
  feet 
  

   the 
  dorsal 
  lamella 
  gradually 
  diminishes, 
  so 
  that 
  at 
  the 
  fourth 
  

   from 
  the 
  posterior 
  pinnate 
  process 
  both 
  lamellae 
  are 
  much 
  

   reduced, 
  and 
  the 
  capillary 
  bristles 
  thus 
  rendered 
  conspicuous. 
  

   Posteriorly 
  the 
  lobes 
  of 
  the 
  feet 
  diminish 
  greatly, 
  whilst 
  the 
  

   dorsal 
  bristles 
  become 
  longer 
  and 
  so 
  slender 
  as 
  to 
  be 
  hair- 
  

   like. 
  Ventrally 
  hooks 
  take 
  the 
  place 
  of 
  the 
  inferior 
  bristles 
  

   from 
  the 
  fifteenth 
  foot 
  backward. 
  In 
  this 
  form 
  the 
  pinnate 
  

   or 
  papillose 
  cirri 
  (PI. 
  VI. 
  fig. 
  1, 
  /.) 
  were 
  sparsely 
  covered 
  

  

  Ann. 
  & 
  Mna. 
  N. 
  Hist, 
  !Ser. 
  8. 
  Vol. 
  .xiii. 
  (j 
  

  

  