﻿30 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.44. 
  

  

  Whether 
  or 
  not 
  the 
  bases 
  of 
  the 
  tentacles 
  are 
  laterally 
  compressed 
  

   depends 
  on 
  how 
  crowded 
  they 
  are; 
  in 
  our 
  intermediate 
  specimen 
  

   they 
  arc 
  noticeably 
  flattened, 
  in 
  the 
  largest 
  hardly 
  at 
  all 
  so. 
  This 
  

   may 
  be 
  partly 
  indi^ddllal 
  variation, 
  partly 
  accidental. 
  

  

  The 
  previous 
  records 
  of 
  P. 
  ladea 
  are 
  from 
  Massachusetts 
  Bay 
  (A. 
  

   Agassiz), 
  off 
  the 
  coast 
  of 
  Nova 
  Scotia 
  (Ilaeckel), 
  between 
  Iceland 
  

   and 
  Ireland 
  (Haeckel), 
  west 
  coast 
  of 
  Greenland 
  (Levinsen), 
  and 
  

   Barents 
  Sea(Linko). 
  

  

  Family 
  MITROCOMIDAE 
  Haeckel 
  (Torrey, 
  1909; 
  Browne, 
  1910). 
  

   Family 
  LAFOEIDAE 
  Maas 
  (1905). 
  

  

  Mayer 
  (1910) 
  does 
  not 
  recognize 
  the 
  structure 
  of 
  the 
  sense 
  organs 
  

   as 
  a 
  family 
  character; 
  but 
  like 
  Maas 
  (1905), 
  Torrey 
  (1909), 
  and 
  

   Browne 
  (1910), 
  I 
  believe 
  that 
  the 
  group 
  characterized 
  by 
  open 
  sense- 
  

   pits 
  in 
  the 
  velum 
  is 
  a 
  natural 
  one, 
  and, 
  as 
  Torrey 
  has 
  pointed 
  out, 
  the 
  

   best 
  available 
  name 
  is 
  Mitrocomidae. 
  

  

  Among 
  the 
  interesting 
  "finds" 
  of 
  the 
  collection 
  is 
  the 
  discovery 
  

   that 
  the 
  large 
  conspicuous 
  medusa 
  so 
  common 
  in 
  Puget 
  Sound, 
  first 
  

   described 
  by 
  A. 
  Agassiz 
  as 
  Laodice 
  cellularia, 
  and 
  recently 
  redescribed 
  

   from 
  mature 
  specimens 
  by 
  Murbach 
  and 
  Shearer 
  (1903) 
  as 
  Thau- 
  

   mantias 
  cellularia, 
  has 
  open 
  sense 
  pits 
  in 
  the 
  velum, 
  and 
  therefore 
  is 
  

   not 
  a 
  Thaumantias 
  at 
  all, 
  but 
  belongs 
  to 
  the 
  Mitrocomidae. 
  But 
  it 
  

   does 
  not 
  fit 
  in 
  any 
  of 
  the 
  genera 
  of 
  the 
  family 
  recognized 
  by 
  Browne 
  

   (1910), 
  for 
  though 
  it 
  has 
  numerous 
  sense 
  pits 
  without 
  ocelli, 
  like 
  

   Mitrocoma, 
  it 
  differs 
  from 
  the 
  latter 
  in 
  lacking 
  marginal 
  curi. 
  And 
  

   inasmuch 
  as 
  there 
  are 
  at 
  least 
  four 
  species 
  of 
  Mitrocoma, 
  as 
  well 
  as 
  one 
  

   of 
  Mitrocomella 
  with 
  cirri, 
  the 
  difference 
  warrants 
  the 
  establishment 
  

   of 
  a 
  new 
  genus, 
  Ilalistaura. 
  Except 
  for 
  the 
  sense-organs, 
  our 
  scries 
  

   agrees 
  with 
  the 
  earlier 
  accounts 
  of 
  cellularia 
  even 
  to 
  minute 
  details. 
  

  

  HALISTAURA, 
  new 
  genus. 
  

  

  Mitrocomidae 
  with 
  4 
  radial 
  canals; 
  with 
  numerous 
  open 
  sensory 
  

   pits; 
  without 
  marginal 
  cirri. 
  

  

  Type. 
  — 
  Halistaura 
  cellularia 
  A. 
  Agassiz. 
  

  

  HALISTAURA 
  CELLULARIA 
  (A. 
  Agassiz). 
  

  

  Laodice 
  cellularia 
  A. 
  Agassiz, 
  ISGo, 
  p. 
  127, 
  figs. 
  195, 
  196. 
  

  

  Thaumantias 
  cellularia 
  Haeckel, 
  1879, 
  p. 
  129. 
  — 
  Murbach 
  and 
  Shearer, 
  1903» 
  

   p. 
  172, 
  pi. 
  17, 
  fig. 
  2, 
  26.— 
  Mayer, 
  1910, 
  p. 
  199. 
  

  

  Station 
  4754, 
  off 
  Southern 
  Alaska, 
  October, 
  1905, 
  surface; 
  7 
  speci- 
  

   mens 
  40-50 
  mm. 
  in 
  diameter. 
  Also 
  several 
  specimens 
  from 
  Puget 
  Sound. 
  

  

  None 
  of 
  the 
  specimens 
  are 
  perfect, 
  most 
  of 
  them 
  being 
  flattened 
  

   out, 
  but 
  several 
  of 
  them 
  are 
  in 
  sufficiently 
  good 
  anatomical 
  condition 
  

   for 
  individual 
  quadrants 
  of 
  the 
  margin 
  to 
  be 
  studied. 
  

  

  The 
  descriptions 
  of 
  this 
  species 
  by 
  L. 
  Agassiz 
  and 
  by 
  Murbach 
  and 
  

   Shearer 
  cover 
  two 
  successive 
  stages 
  in 
  its 
  development, 
  the 
  former 
  

  

  