﻿406 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.44. 
  

  

  cliicfly 
  on 
  the 
  basis 
  of 
  this 
  habit 
  of 
  cementing 
  together 
  the 
  muddy 
  

   sand 
  that 
  Quatrefages 
  (1865) 
  observed 
  in 
  specimens 
  from 
  North 
  

   America 
  that 
  ho 
  gave 
  the 
  name 
  SijMnculus 
  csementarius 
  to 
  these 
  

   specimens. 
  The 
  tubes 
  of 
  cement 
  are 
  usually 
  slightly 
  curved, 
  and 
  

   are 
  marked 
  on 
  the 
  exterior 
  at 
  regular 
  intervals 
  by 
  annular 
  furrows. 
  

   (PI. 
  60, 
  fig. 
  10.) 
  

  

  The 
  color 
  of 
  the 
  animal 
  varies 
  from 
  a 
  very 
  dark 
  brown 
  or 
  a 
  grayish- 
  

   brown 
  (variety 
  tuhicola), 
  orange-brown 
  or 
  yellowish-brown 
  (variety 
  

   fusca) 
  to 
  white 
  (variety 
  alha) 
  . 
  The 
  dark 
  brown 
  specimens 
  from 
  cer- 
  

   tain 
  regions 
  have 
  a 
  decidedly 
  purple 
  hue, 
  which 
  is 
  especially 
  common 
  

   in 
  the 
  grayish-brown 
  individuals 
  that 
  live 
  in 
  Pectinaria 
  tubes. 
  

  

  Light 
  yellowish-brown 
  or 
  orange-brown 
  is 
  the 
  color 
  of 
  the 
  widely 
  

   distributed 
  typical 
  form, 
  as 
  seen 
  in 
  specimens 
  from 
  Labrador, 
  the 
  

   coast 
  of 
  Nova 
  Scotia, 
  from 
  off 
  Eastport, 
  off 
  Point 
  Judith, 
  and 
  farther 
  

   south. 
  The 
  color 
  of 
  the 
  local 
  varieties 
  will 
  be 
  mentioned 
  in 
  the 
  

   descriptions 
  that 
  are 
  to 
  follow. 
  

  

  There 
  are 
  16 
  tentacles 
  (pi. 
  60, 
  fig. 
  12) 
  in 
  the 
  specimens 
  from 
  com- 
  

   paratively 
  shallow 
  waters 
  off 
  the 
  coast 
  of 
  Maine 
  and 
  Massachusetts, 
  

   but 
  the 
  number 
  m 
  other 
  localities 
  is 
  20, 
  24, 
  or 
  26; 
  20 
  occur 
  in 
  speci- 
  

   mens 
  from 
  off 
  Nova 
  Scotia 
  (stations 
  44-46); 
  24 
  in 
  individuals 
  from 
  

   300 
  fathoms 
  oft' 
  Norfolk, 
  Vkginia 
  (station 
  898) 
  ; 
  26 
  in 
  specimens 
  from 
  

   south 
  of 
  the 
  Grand 
  Banks 
  of 
  Newfoundland 
  (station 
  2437). 
  The 
  

   number 
  in 
  two 
  specimens 
  figured 
  by 
  Theel 
  (1904) 
  is 
  respectively 
  16 
  

   and 
  26, 
  and 
  I 
  find 
  26 
  in 
  a 
  specimen 
  from 
  the 
  east 
  coast 
  of 
  Sweden 
  

   sent 
  to 
  me 
  by 
  Professor 
  Theel. 
  

  

  A 
  zone 
  of 
  recurved 
  hooks, 
  disposed 
  irregularly, 
  occurs 
  a 
  short 
  

   distance 
  behind 
  the 
  tentacles 
  (fig. 
  9). 
  

  

  Prominent 
  papillae 
  cover 
  the 
  anterior 
  part 
  of 
  the 
  trunk 
  and 
  the 
  

   proximal 
  part 
  of 
  the 
  introvert 
  (pi. 
  60, 
  fig. 
  11); 
  elsewhere 
  the 
  body 
  is 
  

   provided 
  with 
  minute 
  papillse 
  which 
  are 
  variable 
  in 
  size, 
  abundance, 
  

   and 
  distribution 
  in 
  the 
  different 
  varieties. 
  

  

  The 
  characteristic 
  holdfasts 
  (Haftpapillen), 
  or 
  papillae 
  crowned 
  

   with 
  triangular, 
  arrow-shaped, 
  chitinous 
  hooks 
  pointing 
  forward, 
  

   occur 
  in 
  a 
  wide 
  band 
  (fig. 
  9) 
  which 
  extends 
  from 
  a 
  little 
  behind 
  the 
  

   middle 
  of 
  the 
  trunk 
  backward 
  nearly 
  to 
  the 
  posterior 
  end, 
  which 
  in 
  

   indiAdduals 
  that 
  live 
  in 
  shells 
  or 
  tubes 
  with 
  smooth 
  walls 
  is 
  smooth, 
  

   or 
  covered 
  with 
  minute 
  papillae, 
  although 
  specimens 
  from 
  tubes 
  of 
  

   cement 
  usually 
  have 
  rather 
  promment 
  papUlse 
  upon 
  the 
  posterior 
  

   extremity 
  of 
  the 
  body. 
  The 
  holdfasts 
  are 
  variable 
  in 
  size, 
  shape, 
  

   and 
  color; 
  especially 
  is 
  this 
  true 
  of 
  the 
  varieties 
  gracilis 
  and 
  canadensis. 
  

   The 
  shape 
  of 
  the 
  chitinous 
  cap 
  is 
  typically 
  like 
  an 
  inverted 
  U 
  or 
  V. 
  

   The 
  variety 
  alha, 
  which 
  is 
  found 
  in 
  gasteropod 
  shells 
  has 
  U-shaped 
  

   holdfasts; 
  those 
  of 
  the 
  thick-skinned 
  variety 
  tuhicola, 
  mhabitants 
  of 
  

   tubes 
  of 
  cement, 
  are 
  in 
  general 
  more 
  pointed. 
  

  

  