﻿STUDIES 
  ON 
  THE 
  CYCLOSTOMATOUS 
  BRYOZOA 
  

  

  By 
  Ferdinand 
  Canu 
  

  

  Of 
  Versailles, 
  France 
  

  

  AND 
  

  

  Ray 
  S. 
  Bassler 
  

  

  Of 
  Washington, 
  District 
  of 
  Columbia 
  

  

  The 
  present 
  paper 
  is 
  our 
  second 
  contribution 
  to 
  the 
  above 
  subject, 
  

   the 
  first 
  having 
  been 
  published 
  in 
  1922 
  x 
  under 
  the 
  subtitle 
  of 
  "Fossil 
  

   and 
  Recent 
  Parallelata 
  and 
  Rectangulata." 
  As 
  explained 
  in 
  this 
  

   first 
  paper, 
  our 
  efforts 
  are 
  especially 
  directed, 
  first, 
  to 
  the 
  study 
  of 
  the 
  

   internal 
  structure 
  of 
  these 
  organisms 
  by 
  means 
  of 
  thin 
  sections 
  in 
  

   order 
  to 
  determine 
  the 
  method 
  of 
  gemmation 
  and 
  the 
  occurrence 
  and 
  

   structure 
  of 
  the 
  various 
  kinds 
  of 
  tubes, 
  and, 
  second, 
  to 
  the 
  function 
  

   of 
  reproduction 
  as 
  brought 
  out 
  by 
  the 
  ovicells. 
  Cyclostomatous 
  

   bryozoa 
  are 
  extremely 
  abundant 
  in 
  certain 
  Mesozoic 
  rocks; 
  indeed, 
  

   they 
  form 
  almost 
  the 
  entire 
  bryozoan 
  fauna 
  of 
  most 
  formations 
  

   before 
  the 
  Upper 
  Cretaceous. 
  

  

  2. 
  LOWER 
  CRETACEOUS 
  CYCLOSTOMATOUS 
  BRYOZOA 
  

  

  The 
  Cretaceous 
  Cyclostomata 
  have 
  received 
  attention 
  from 
  many 
  

   authors, 
  but 
  particularly 
  through 
  the 
  work 
  of 
  D'Orbigny 
  in 
  volume 
  

   5 
  of 
  the 
  Paleontologie 
  francaise 
  and 
  Gregory 
  in 
  his 
  two 
  volumes 
  of 
  

   the 
  Catalogue 
  of 
  the 
  Cretaceous 
  Bryozoa 
  in 
  the 
  British 
  Museum. 
  

   Both 
  of 
  these 
  authors, 
  in 
  fact 
  most 
  previous 
  students, 
  have 
  adoped 
  

   an 
  artificial 
  classification 
  which 
  in 
  the 
  number 
  of 
  genera 
  proposed 
  

   and 
  the 
  slight 
  reasons 
  for 
  their 
  existence 
  is 
  amazing. 
  Gregory's 
  two 
  

   volumes 
  are 
  valuable 
  contributions 
  to 
  the 
  bibliographic 
  and 
  histori- 
  

   cal 
  sides 
  of 
  the 
  subject 
  and 
  his 
  studies 
  of 
  the 
  internal 
  structure 
  mark 
  

   a 
  great 
  advance 
  in 
  the 
  science. 
  Our 
  studies 
  carry 
  Gregory's 
  efforts 
  

   still 
  further; 
  in 
  fact, 
  our 
  main 
  object 
  has 
  been 
  an 
  effort 
  to 
  determine 
  

   the 
  natural 
  generic 
  characters 
  in 
  this 
  group. 
  

  

  We 
  have 
  undertaken 
  the 
  study 
  of 
  the 
  Lower 
  Cretaceous 
  Cyclosto- 
  

   mata 
  at 
  this 
  time 
  due 
  to 
  our 
  possession 
  of 
  ample, 
  well-preserved 
  

  

  1 
  Proc. 
  U. 
  S. 
  Nat. 
  Mus., 
  vol. 
  61, 
  pp. 
  1-160, 
  28 
  pis., 
  40 
  text 
  figs. 
  

  

  No. 
  2593.— 
  Proceedings 
  U. 
  S. 
  National 
  Museum, 
  Vol. 
  67, 
  Art. 
  2!. 
  

  

  53648—26 
  1 
  1 
  

  

  