﻿aht. 
  21 
  CYCLOSTOMATOUS 
  BRYOZOA 
  CANU 
  AND 
  BASSLER 
  81 
  

  

  shorter 
  and 
  shorter; 
  a 
  certain 
  number 
  aborted 
  (by 
  the 
  disappearance 
  

   of 
  the 
  polypide), 
  closed 
  by 
  a 
  calcareous 
  pellicule 
  and 
  become 
  the 
  

   dactylethrae. 
  An 
  examination 
  of 
  the 
  extremity 
  of 
  a 
  branch 
  also 
  

   reveals 
  the 
  same 
  heteroporoid 
  structure, 
  This 
  feature 
  has 
  been 
  

   described 
  by 
  D'Orbigny, 
  1852, 
  and 
  by 
  Gregory, 
  1899, 
  who 
  have 
  

   established 
  the 
  family 
  Clausidae 
  upon 
  it. 
  

  

  In 
  transverse 
  section 
  the 
  tubes 
  are 
  polygonal, 
  with 
  thickened 
  

   walls, 
  a 
  little 
  larger 
  toward 
  the 
  periphery. 
  Among 
  the 
  large 
  tubes 
  

   appear 
  smaller 
  tubes 
  irregularly 
  scattered; 
  these 
  are 
  newly 
  formed 
  

   young 
  tubes 
  whose 
  thin 
  base 
  is 
  thus 
  sectioned. 
  The 
  dactylethrae 
  

   appear 
  as 
  smaller 
  tubes 
  visible 
  only 
  at 
  the 
  periphery. 
  

  

  In 
  tangential 
  sections 
  the 
  tubes 
  are 
  polygonal, 
  with 
  thick 
  and 
  

   adjacent 
  walls 
  but 
  in 
  which 
  the 
  interior 
  is 
  rounded. 
  The 
  dactyl- 
  

   ethrae 
  are 
  smaller 
  and 
  their 
  interior 
  remains 
  polygonal. 
  

  

  Affinities. 
  — 
  This 
  is 
  the 
  only 
  species 
  of 
  the 
  Clausidae 
  in 
  which 
  the 
  

   peristomes 
  are 
  grouped 
  in 
  circular 
  zones 
  separated 
  by 
  narrower 
  

   zones 
  of 
  dactylethrae. 
  This 
  simple 
  exterior 
  character 
  is 
  sufficient 
  

   to 
  distinguish 
  it 
  from 
  other 
  species 
  of 
  the 
  Cretaceous 
  and 
  notably 
  

   from 
  Clausa 
  heteropora 
  D'Orbigny, 
  1851, 
  very 
  commonly 
  observed 
  in 
  

   the 
  Cenomanian 
  of 
  Europe, 
  as 
  well 
  as 
  Clausa 
  cranei, 
  new 
  species. 
  

  

  Occurrence. 
  — 
  Lower 
  Cretaceous 
  (Aptian) 
  : 
  Faringdon, 
  England 
  

   (common). 
  

  

  Cotypes.—C&t. 
  No. 
  69935, 
  U.S.N.M. 
  

  

  Genus 
  REPTOCLAUSA 
  D'Orbigny, 
  1853 
  

  

  1S53. 
  Reploclaum 
  D'Orbigny, 
  PalSontologie 
  francaise, 
  Terrain 
  CretacS, 
  vol. 
  5, 
  

   p. 
  887. 
  

  

  Based 
  on 
  historic 
  considerations 
  and 
  the 
  right 
  of 
  priority, 
  Gregory 
  

   in 
  1897 
  classified 
  the 
  species 
  of 
  this 
  genus 
  in 
  Idmonea 
  Lamouroux, 
  

   1821. 
  The 
  zoologists 
  have 
  not 
  yet 
  admitted 
  this 
  classification, 
  which 
  

   would 
  necessitate 
  a 
  complete 
  rearrangement 
  of 
  the 
  bibliography 
  

   relative 
  to 
  Idmonea. 
  We 
  have 
  nothing 
  to 
  add 
  to 
  this 
  discussion, 
  and 
  

   while 
  awaiting 
  a 
  decision 
  on 
  the 
  question 
  as 
  to 
  whether 
  Idmonea 
  was 
  

   clearly 
  defined 
  we 
  will 
  continue 
  to 
  follow 
  the 
  principle 
  of 
  least 
  change. 
  

   We 
  will 
  preserve, 
  therefore, 
  D'Orbigny's 
  name 
  for 
  the 
  curious 
  forms 
  

   herein 
  described. 
  

  

  The 
  tubes 
  are 
  grouped 
  in 
  idmoneiform 
  fascicles, 
  but 
  the 
  tubes 
  do 
  

   not 
  have 
  adjacent 
  peristomes. 
  The 
  spaces 
  between 
  the 
  fascicles 
  are 
  

   of 
  real 
  tubes 
  or 
  aborted. 
  They 
  are 
  ramified 
  on 
  the 
  tubes 
  of 
  the 
  fas- 
  

   cicles 
  primitively 
  formed 
  and 
  their 
  coalescence 
  engenders 
  new 
  fasci- 
  

   cles. 
  At 
  the 
  exterior 
  they 
  are 
  visible 
  or 
  invisible, 
  according 
  to 
  the 
  

   thickness 
  of 
  the 
  tissue. 
  

  

  