﻿Gaily 
  Marine 
  Laboratory^ 
  St. 
  Amhrws. 
  105 
  

  

  M. 
  elisabet 
  ha), 
  then 
  turns 
  backward 
  to 
  the 
  edge 
  of 
  the 
  denti- 
  

   culated 
  membrane 
  of 
  the 
  fourth 
  setigerous 
  segment. 
  Tlie 
  

   latter, 
  the 
  lower 
  lip, 
  and 
  the 
  Lateral 
  folds 
  thus 
  form 
  a 
  kind 
  

   of 
  base 
  or 
  sheath 
  for 
  all 
  the 
  parts 
  in 
  front. 
  The 
  transverse 
  

   and 
  free 
  fold 
  just 
  alluded 
  to 
  has 
  about 
  a 
  dozen 
  denticulatioas 
  

   of 
  nearly 
  equal 
  size 
  on 
  its 
  free 
  oi' 
  anterior 
  edge. 
  

  

  The 
  body 
  , 
  is 
  somewhat 
  clavate, 
  broad 
  at 
  the 
  branchial 
  

   region, 
  and 
  gently 
  tapering 
  to 
  the 
  slender 
  posterior 
  extremity, 
  

   wliifli 
  is 
  characterised 
  amongst 
  the 
  Ampharetidse 
  by 
  its 
  

   great 
  lengthy 
  no 
  less 
  than 
  about 
  fifty 
  segments 
  occurring 
  

   in 
  it. 
  The 
  anus 
  is 
  terminal, 
  comparatively 
  lai'ge 
  for 
  the 
  

   size 
  of 
  the 
  region, 
  and 
  in 
  the 
  only 
  example 
  in 
  which 
  the 
  

   part 
  is 
  apparently 
  complete 
  a 
  few 
  short 
  papillcC 
  occurred 
  

   on 
  the 
  edge. 
  Above 
  aud 
  beneath 
  the 
  anus 
  is 
  a 
  vertical 
  slit 
  

   with 
  the 
  lateral 
  edge 
  projecting 
  on 
  each 
  side. 
  The 
  dorsal 
  

   surface 
  of 
  the 
  body 
  is 
  rounded 
  and 
  smooth, 
  whilst 
  the 
  

   ventral 
  surface 
  is 
  marked 
  anteriorly, 
  as 
  far 
  as 
  the 
  fourteenth 
  

   bristle-bundle, 
  by 
  the 
  glandular 
  thickenings 
  in 
  each 
  segment 
  ; 
  

   thereafter 
  a 
  median 
  groove 
  is 
  continued 
  to 
  the 
  slender 
  

   region 
  near 
  the 
  tip 
  of 
  the 
  tail. 
  

  

  The 
  first 
  three 
  bristle-bundles 
  are 
  small, 
  and 
  form 
  a 
  

   slightly 
  oblique 
  row 
  in 
  the 
  preparations 
  along 
  the 
  edge 
  of 
  

   the 
  flap 
  between 
  the 
  mouth 
  and 
  the 
  denticulated 
  border 
  on 
  the 
  

   dorsum 
  of 
  the 
  fourth 
  bristled 
  segment 
  ; 
  these 
  have 
  no 
  evident 
  

   setigerous 
  process, 
  since 
  they 
  are 
  immersed 
  in 
  the 
  tissues 
  

   of 
  the 
  region. 
  The 
  following 
  fifteen 
  pairs 
  have, 
  when 
  fully 
  

   developed, 
  a 
  prominent 
  and 
  somewhat 
  conical 
  setigerous 
  

   process, 
  from 
  which 
  the 
  long 
  pale 
  golden 
  bristles 
  project 
  

   either 
  transversely 
  or 
  in 
  a 
  slightly 
  backwai'd 
  direction. 
  The 
  

   bristles 
  have 
  long 
  finely 
  striated 
  shafts 
  and 
  slightly 
  curved 
  

   and 
  winged 
  tips, 
  which 
  taper 
  to 
  a 
  fine 
  point. 
  A 
  shorter 
  

   series 
  occurs 
  amongst 
  the 
  foregoing, 
  their 
  finely 
  tapered 
  

   tips 
  falling 
  short 
  of 
  the 
  longer 
  by 
  a 
  considerable 
  interval. 
  

  

  Between 
  the 
  basal 
  region 
  of 
  the 
  branchise 
  on 
  each 
  side 
  and 
  

   the 
  denticulated 
  margin 
  of 
  the 
  dorsal 
  collar 
  is 
  a 
  powerful 
  

   hook 
  which, 
  in 
  the 
  preparations, 
  is 
  generally 
  conspicuous, 
  

   the 
  point 
  being 
  directed 
  backward 
  and 
  downward. 
  It 
  has 
  

   a 
  broad 
  flattened 
  base 
  and 
  shaft, 
  the 
  latter 
  widening 
  as 
  it 
  

   proceeds 
  upward 
  from 
  the 
  base 
  to 
  about 
  half 
  its 
  length, 
  

   then 
  narrows 
  distally, 
  the 
  tip 
  forming 
  a 
  sharp 
  hook 
  which 
  

   curves 
  to 
  the 
  front. 
  Along 
  the 
  dorsal 
  or 
  convex 
  edge 
  of 
  the 
  

   curve 
  a 
  considerable 
  thickening 
  of 
  the 
  brittle 
  chitinous 
  

   tissue 
  occurs, 
  and 
  this 
  part 
  is 
  perforated 
  by 
  a 
  canal 
  con- 
  

   taining 
  granular 
  contents, 
  and 
  in 
  connection 
  with 
  a 
  gland, 
  

   also 
  granular, 
  at 
  the 
  side 
  of 
  the 
  shaft. 
  The 
  canal 
  opens 
  on 
  

   the 
  convex 
  side 
  of 
  the 
  organ 
  a 
  little 
  short 
  of 
  the 
  tip. 
  The 
  

  

  