﻿.ibt. 
  zi 
  CYCLOSTOMATOUS 
  BRYOZOA 
  CANU 
  AND 
  BASSLER 
  89 
  

  

  SIPHODICTYUM 
  IRREGULARE, 
  new 
  species 
  

  

  Plate 
  14, 
  figs. 
  1-11 
  

  

  Description. 
  — 
  The 
  zoarium 
  is 
  cylindrical, 
  slender, 
  dichotomously 
  

   branched. 
  On 
  the 
  cellular 
  face 
  the 
  orifices 
  are 
  arranged 
  in 
  irregular 
  

   quincunx 
  or 
  in 
  transverse 
  lines 
  interrupted 
  in 
  the 
  middle; 
  the 
  peri- 
  

   stomes 
  are 
  salient, 
  thick, 
  adjacent, 
  or 
  scattered; 
  they 
  are 
  separated 
  

   by 
  groups 
  of 
  2 
  to 
  4 
  vacuoles. 
  On 
  the 
  dorsal 
  face 
  the 
  vacuoles 
  occur 
  

   at 
  the 
  base 
  of 
  sulci 
  of 
  little 
  depth, 
  arranged 
  longitudinally 
  and 
  

   obliquely. 
  At 
  the 
  extremity 
  of 
  the 
  branches 
  the 
  peristomes 
  occur 
  

   entirely 
  around 
  the 
  colony. 
  The 
  cellular 
  groups 
  are 
  separated 
  by 
  

   noncellular 
  spaces 
  showing 
  only 
  vacuoles. 
  The 
  ovicell 
  is 
  a 
  large, 
  

   very 
  convex 
  sack 
  placed 
  in 
  the 
  noncellular 
  portion 
  of 
  the 
  zoarium. 
  

  

  Measurements. 
  — 
  Diameter 
  of 
  orifice, 
  0.08 
  mm.; 
  zooecial 
  diameter, 
  

   0.12 
  mm.; 
  distance 
  of 
  orifices, 
  0.28-0.32 
  mm.; 
  diameter 
  of 
  largest 
  

   branches, 
  0.65 
  mm. 
  

  

  Structure. 
  — 
  The 
  longitudinal 
  section 
  of 
  the 
  cellular 
  branches 
  shows 
  

   on 
  the 
  frontal 
  a 
  thick 
  peripheral 
  epitheca 
  perforated 
  by 
  vacuoles, 
  

   short 
  cylindrical 
  tubes 
  with 
  triparietal 
  gemmation 
  around 
  a 
  central 
  

   axis, 
  and 
  dorsal 
  tubes 
  analogous 
  but 
  aborted 
  and 
  engendering 
  the 
  

   vacuoles. 
  

  

  The 
  longitudinal 
  section 
  of 
  the 
  noncellular 
  branches 
  show 
  identi- 
  

   cal 
  characters, 
  but 
  all 
  the 
  tubes 
  are 
  aborted 
  and 
  engender 
  numerous 
  

   vacuoles. 
  

  

  The 
  transverse 
  section 
  shows 
  a 
  very 
  thick 
  epitheca 
  perforated 
  by 
  

   vacuoles, 
  by 
  complete 
  tubes, 
  or 
  by 
  incomplete 
  tubes. 
  

  

  The 
  tangential 
  section 
  of 
  the 
  cellular 
  face 
  shows 
  the 
  orbicular 
  

   orifices 
  and 
  a 
  variable 
  number 
  of 
  small 
  vacuoles 
  very 
  irregularly 
  

   arranged 
  and 
  immersed 
  in 
  a 
  thick 
  epitheca. 
  Irregular 
  veinules 
  indi- 
  

   cate 
  the 
  presence 
  of 
  the 
  sulci. 
  The 
  tangential 
  section 
  of 
  the 
  non- 
  

   cellular 
  portions 
  exhibit 
  very 
  small 
  vacuoles 
  arranged 
  in 
  quincunx 
  

   and 
  immersed 
  in 
  a 
  thick 
  epitheca 
  in 
  which 
  the 
  veinules 
  are 
  indicated 
  

   by 
  the 
  darker 
  portions. 
  

  

  This 
  species 
  has 
  afforded 
  sections 
  closer 
  to 
  those 
  of 
  Gregory, 
  1899 
  

   (p. 
  364); 
  but 
  the 
  walls 
  of 
  the 
  adventitious 
  tubes 
  are 
  much 
  thicker 
  

   and 
  seem 
  to 
  indicate 
  vacuoles 
  rather 
  than 
  mesopores. 
  

  

  The 
  orifices 
  are 
  arranged 
  in 
  transverse 
  rows, 
  interrupted 
  or 
  in 
  quin- 
  

   cunx. 
  On 
  the 
  same 
  zoarium 
  there 
  are 
  large 
  cellular 
  spaces 
  with 
  peri- 
  

   stomes 
  on 
  a 
  single 
  side, 
  but 
  they 
  alternate 
  with 
  the 
  large 
  noncellular 
  

   spaces. 
  At 
  the 
  extremity 
  of 
  the 
  branches 
  the 
  orifices 
  are 
  disposed 
  

   entirely 
  around 
  the 
  colony. 
  The 
  lateral 
  dichotomisations 
  are 
  always 
  

   verv 
  short. 
  

  

  