﻿236 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.96 
  

  

  band 
  and 
  three 
  lateral, 
  equidistantly 
  spaced. 
  The 
  bands, 
  1.5 
  to 
  

   2 
  mm. 
  broad, 
  represent 
  concentrations 
  of 
  longitudinal 
  muscle 
  fibers, 
  

   which 
  gradually 
  thin 
  out 
  on 
  the 
  sides 
  of 
  the 
  bands. 
  The 
  skin 
  is 
  

   beset. 
  with 
  small, 
  unequal, 
  subcircular 
  and 
  elliptical 
  glandular 
  thick- 
  

   enings 
  arranged 
  in 
  transverse 
  close-set 
  lines. 
  At 
  posterior 
  end 
  there 
  

   is 
  an 
  area 
  of 
  greatly 
  enlarged 
  papillae. 
  Coelomic 
  surface 
  of 
  body 
  

   wall 
  smooth; 
  innermost 
  layer 
  of 
  slightly 
  oblique 
  muscle 
  fibers 
  very 
  

   thin, 
  uniform, 
  not 
  mterrupted 
  by 
  the 
  longitudinal 
  thickenings 
  of 
  

   the 
  middle 
  layer. 
  

  

  Setae 
  2, 
  close 
  together, 
  and 
  close 
  to 
  the 
  mouth. 
  Sometimes 
  two 
  

   setae 
  occupy 
  one 
  of 
  the 
  sheaths, 
  with 
  a 
  single 
  normal 
  one 
  in 
  the 
  

   other. 
  There 
  is 
  an 
  interbasal 
  muscle 
  uniting 
  top 
  of 
  the 
  sheaths. 
  This 
  

   passes 
  through 
  a 
  loop 
  in 
  the 
  dorsoventral 
  blood 
  vessel. 
  

  

  Nephridia 
  4, 
  variable 
  in 
  size. 
  In 
  the 
  type 
  the 
  anterior 
  pair 
  is 
  

   smaller 
  than 
  the 
  posterior, 
  but 
  in 
  another 
  specimen 
  the 
  anterior 
  

   pair 
  is 
  the 
  larger 
  and 
  the 
  four 
  are 
  about 
  five 
  times 
  the 
  length 
  of 
  those 
  

   of 
  type. 
  They 
  have 
  the 
  same 
  terminal 
  slender 
  portion, 
  which 
  can 
  

   undoubtedly 
  be 
  expanded. 
  Both 
  specimens 
  are 
  males. 
  The 
  anterior 
  

   pair 
  is 
  situated 
  posterior 
  to 
  setae 
  about 
  the 
  length 
  of 
  the 
  latter. 
  The 
  

   ciliated 
  funnel 
  has 
  long 
  coiled 
  lips 
  and 
  is 
  attached 
  to 
  the 
  outer 
  side 
  

   of 
  the 
  base 
  of 
  nephridium 
  by 
  a 
  short 
  stalk. 
  In 
  a 
  third 
  specimen 
  the 
  

   nephridia 
  are 
  empty 
  and 
  reduced 
  to 
  filaments 
  slightly 
  expanded 
  at 
  

   base. 
  In 
  a 
  full-grown 
  female 
  (Tomales 
  Bay) 
  the 
  nephridia 
  are 
  20 
  

   mm. 
  long, 
  slender, 
  and 
  contain 
  numerous 
  eggs 
  (June 
  7), 
  0.08 
  to 
  0.09 
  

   mm. 
  in 
  diameter. 
  

  

  Anal 
  vesicles 
  2, 
  variable 
  in 
  size, 
  capable 
  of 
  great 
  extension. 
  Each 
  

   is 
  fastened 
  to 
  body 
  wall 
  about 
  5 
  mm. 
  laterally 
  from 
  the 
  anus 
  by 
  one 
  

   or 
  two 
  mesenteries 
  and 
  ventrally 
  by 
  another 
  pair 
  close 
  to 
  nerve. 
  

   Into 
  these, 
  which 
  appear 
  hollow, 
  extends 
  a 
  short 
  diverticulum 
  of 
  

   the 
  vesicle. 
  There 
  are 
  scattered, 
  very 
  tiny, 
  ciliated 
  funnels. 
  The 
  

   well-preserved 
  female 
  from 
  Tomales 
  Bay 
  has 
  vesicles 
  that 
  extend 
  as 
  

   far 
  forward 
  as 
  the 
  large 
  posterior 
  nephi'idia 
  and 
  lack 
  the 
  basal 
  diver- 
  

   ticulum 
  found 
  in 
  the 
  male. 
  

  

  Alimentary 
  canal. 
  The 
  pharynx 
  extends 
  to 
  the 
  sharp 
  bend 
  shown 
  

   in 
  the 
  illustration, 
  followed 
  by 
  the 
  esophagus. 
  The 
  gizzard 
  is 
  short 
  

   and 
  the 
  stomach 
  relatively 
  long, 
  but 
  there 
  is 
  bound 
  to 
  be 
  variation 
  in 
  

   different 
  specimens 
  o^ving 
  to 
  the 
  accidents 
  of 
  preservation. 
  The 
  

   intestine 
  proper 
  starts 
  just 
  back 
  of 
  the 
  ring 
  blood 
  vessel, 
  at 
  the 
  

   beginning 
  of 
  the 
  ciliated 
  groove, 
  which 
  soon 
  becomes 
  differentiated 
  

   into 
  the 
  siphon. 
  Even 
  in 
  the 
  carefully 
  hardened 
  specimen 
  from 
  To- 
  

   males 
  Bay 
  the 
  intestinal 
  wall 
  is 
  delicate 
  and 
  transparent. 
  The 
  

   length 
  is 
  difficult 
  to 
  measure 
  on 
  account 
  of 
  unequal 
  contraction. 
  The 
  

   siphonal 
  part 
  is 
  on 
  the 
  order 
  of 
  100 
  mm. 
  in 
  length 
  and 
  the 
  postsiphonal 
  

   125 
  mm. 
  (length 
  of 
  specimen, 
  40 
  mm.). 
  Throughout 
  its 
  length 
  the 
  

   intestine 
  is 
  stuff 
  ed 
  with 
  small 
  unequal 
  (1-2 
  mm.) 
  ellipsoidal 
  mud 
  pel- 
  

  

  