﻿428 
  PBOCEEDINGS 
  OF 
  THE 
  XATIOXAL 
  MUSEUM. 
  

  

  breadth 
  near 
  posterior 
  end, 
  2.50; 
  length 
  of 
  median 
  segments, 
  0.25; 
  

   breadth 
  of 
  head, 
  anterior 
  end, 
  0.40; 
  breadth 
  of 
  head, 
  base, 
  1.30; 
  length 
  

   of 
  head, 
  0.80. 
  Body 
  lanceolate, 
  depressed, 
  articulate. 
  Head 
  short- 
  

   triangular, 
  obtuse, 
  with 
  median, 
  terminal 
  pore, 
  and 
  two 
  flat, 
  leaflike 
  

   flaps 
  (bothria) 
  on 
  lateral 
  margins, 
  separated 
  from 
  each 
  other 
  on 
  flat 
  

   surface 
  by 
  a 
  broad, 
  shallow 
  sulcus. 
  First 
  segment 
  much 
  broader 
  than 
  

   head, 
  its 
  posterior 
  border 
  much 
  broader 
  than 
  its 
  anterior 
  border; 
  sub- 
  

   sequent 
  segments 
  increasing 
  in 
  breadth 
  rapidly, 
  their 
  posterior 
  borders 
  

   greater 
  than 
  their 
  anterior, 
  until 
  maximum 
  breadth 
  is 
  attained; 
  lat- 
  

   eral 
  margins 
  of 
  anterior 
  segments 
  with 
  a 
  distinct 
  emargination, 
  which 
  

   character 
  also 
  appertains 
  to 
  the 
  bothrial 
  flaps 
  of 
  one 
  of 
  the 
  specimens 
  

   (Fig. 
  4). 
  

  

  »S'. 
  (iimorphu.s 
  is 
  described 
  as 
  having 
  in 
  the 
  larA^al 
  state 
  a 
  longi- 
  

   tudinal 
  median 
  furrow 
  on 
  each 
  face. 
  These 
  specimens 
  do 
  not 
  exhibit 
  

   this 
  character; 
  neither 
  do 
  they 
  have 
  anything 
  that 
  can 
  properly 
  be 
  

   called 
  a 
  costa 
  dividing 
  the 
  two 
  bothria. 
  I 
  do 
  not 
  find 
  any 
  mention 
  

   of 
  emarginations 
  on 
  the 
  segments 
  in 
  any 
  of 
  the 
  descriptions 
  of 
  S. 
  dimor- 
  

   jyhus 
  to 
  which 
  I 
  have 
  access. 
  On 
  account 
  of 
  these 
  ditterences 
  I 
  refer 
  

   these 
  specimens 
  to 
  S. 
  dimorphns 
  with 
  some 
  doubt. 
  Diesing 
  records 
  S. 
  

   d 
  imorjjh 
  11. 
  s 
  from 
  the 
  following 
  hosts 
  (genera 
  only 
  giv^en 
  here): 
  Larval 
  

   state 
  from 
  three 
  genera 
  of 
  fish, 
  Gasterostetis, 
  Coitus, 
  and 
  Sahno; 
  one 
  

   bird, 
  Totanus; 
  one 
  seal, 
  Phoca. 
  i^dult 
  state 
  from 
  the 
  following 
  genera 
  

   of 
  birds: 
  Corvus, 
  Becurrirostra, 
  Ardea, 
  Ciconia, 
  Sterna, 
  Colynihus, 
  Podi- 
  

   ceps, 
  Larus, 
  Anas, 
  Mergus, 
  TJria, 
  Alca. 
  The 
  structure 
  of 
  the 
  body 
  resem- 
  

   bles 
  that 
  of 
  the 
  genus 
  Dibothrinm 
  (Fig. 
  5). 
  Beginning 
  with 
  the 
  outer 
  

   layer 
  the 
  successive 
  layers 
  are 
  (1) 
  cuticle, 
  (2) 
  a 
  fibro-granular 
  layer 
  with 
  

   small 
  bundles 
  of 
  longitudinal 
  muscle 
  fibers 
  in 
  the 
  inner 
  part, 
  (3) 
  a 
  layer 
  

   of 
  circular 
  fibers, 
  (4) 
  a 
  glandular 
  muscular 
  layer, 
  with 
  radiating 
  fibers. 
  

   The 
  outer 
  part 
  of 
  this 
  contains 
  the 
  incipient 
  vitellaria, 
  the 
  central 
  part 
  

   contains 
  large 
  bundles 
  of 
  coarse 
  longitudinal 
  muscle-fibers; 
  radiating 
  

   fibers 
  cross 
  the 
  layer 
  separating 
  the 
  bundles 
  of 
  muscles 
  from 
  each 
  

   other 
  and 
  passing 
  between 
  the 
  glandular 
  bodies; 
  (5) 
  a 
  layer 
  of 
  circular 
  

   fibers 
  thicker 
  than 
  (2); 
  (G) 
  a 
  central 
  core 
  surrounded 
  by 
  the 
  layers 
  of 
  

   circular 
  fibers 
  and 
  containing 
  the 
  incipient 
  genitalia 
  embedded 
  in 
  

   granulo-fibrous 
  tissue. 
  In 
  the 
  central 
  core 
  the 
  testes 
  could 
  be 
  made 
  

   out; 
  also 
  a 
  longitudinal 
  vessel 
  (nerve) 
  (Fig. 
  5»). 
  The 
  only 
  part 
  exam- 
  

   ined 
  in 
  sections 
  was 
  the 
  anterior, 
  in 
  which 
  the 
  genitalia 
  were 
  no 
  further 
  

   developed 
  than 
  is 
  indicated 
  in 
  Fig. 
  5. 
  

  

  6. 
  CYATHOCEPHALUS 
  TRUNCATUS 
  Pallas. 
  

   (Plate 
  XX 
  VIII, 
  tigs. 
  6-8.) 
  

  

  Ta'tiia 
  inincata 
  Pallas, 
  1781, 
  Nene 
  Nordiscbe 
  BeitrJige, 
  I, 
  p. 
  105. 
  pi. 
  in, 
  fig. 
  7. 
  

  

  Cephalocotylcum 
  DiESiXG, 
  Syst. 
  Heliu., 
  I, 
  p. 
  620. 
  

  

  Ci/atlwccphahts 
  Iruncafiis 
  Kksslei!, 
  1868, 
  Reitnige 
  zur 
  Fauna 
  des 
  Onega-Sees, 
  

   p. 
  i:i">, 
  pi. 
  VIII, 
  fig. 
  3.— 
  Grimm, 
  Zeitsflirilt 
  f. 
  w. 
  Zool.. 
  XXI, 
  pp. 
  .">02-504.— 
  

   LoNNHKU.i, 
  K.Sv.Miska 
  Vrt.-.\kM(!. 
  Handlingav. 
  XIV, 
  Afd. 
  4, 
  No. 
  9 
  (1889). 
  

  

  