﻿84 
  

  

  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  

  

  tures, 
  short, 
  parietal, 
  sometimes 
  closed 
  by 
  a 
  lamella. 
  The 
  ovicell 
  

   is 
  orbicular, 
  nonsalient, 
  traversed 
  by 
  15 
  tubes. 
  

  

  Measurements. 
  — 
  Diameter 
  of 
  orifice, 
  0.09 
  mm.; 
  diameter 
  of 
  peri- 
  

   stome, 
  0.11 
  mm.; 
  diameter 
  of 
  mesopores, 
  0.04 
  mm.; 
  diameter 
  of 
  

   zoarium, 
  1.25 
  mm. 
  

  

  Structure. 
  — 
  In 
  transverse 
  section 
  the 
  tubes 
  are 
  cylindrical 
  or 
  polyg- 
  

   onal, 
  with, 
  adjacent 
  walls, 
  with 
  regular 
  peripheral 
  gemmation. 
  In 
  

   longitudinal 
  section 
  the 
  tubes 
  are 
  long, 
  cylindrical, 
  narrowed 
  at 
  the 
  

   base, 
  with 
  regular 
  peripheral 
  gemmation 
  in 
  the 
  vicinity 
  of 
  the 
  zoarial 
  

   axis; 
  they 
  are 
  recurved 
  at 
  their 
  extremity. 
  The 
  mesopores 
  are 
  

   parietal, 
  but, 
  as 
  their 
  arrangement 
  around 
  the 
  aperture 
  is 
  irregular, 
  

   they 
  are 
  cut 
  in 
  sections 
  irregularly 
  and 
  present 
  the 
  most 
  varied 
  forms; 
  

  

  Fig. 
  43.—Laterocavea 
  dutempleana 
  D'Orbigny, 
  1853. 
  A. 
  Meridian 
  section, 
  X 
  16, 
  through 
  a 
  growing 
  

   branch, 
  showing 
  the 
  lozenge-shaped 
  areas. 
  B. 
  Longitudinal 
  section, 
  X 
  16, 
  with 
  an 
  accessory 
  exterior 
  

   lamella 
  at 
  the 
  left. 
  C. 
  Meridian 
  section, 
  X 
  16, 
  showing 
  mesopores 
  only 
  in 
  the 
  lateral 
  faces. 
  D. 
  

   Transverse 
  section, 
  X 
  16, 
  through 
  a 
  normal 
  branch. 
  E. 
  Longitudinal 
  section, 
  X 
  16, 
  illustrating 
  the 
  

   cylindrical 
  tubes 
  with 
  triparietal 
  gemmation 
  around 
  a 
  central 
  tube 
  Lower 
  Cretaceous 
  (Aptian): 
  

   Faringdon, 
  England 
  

  

  their 
  walls 
  are 
  very 
  thick. 
  In 
  tangential 
  sections 
  the 
  mesopores 
  are 
  

   very 
  small 
  and 
  surrounded 
  by 
  very 
  thick 
  calcareous 
  tissues. 
  

  

  Affinities. 
  — 
  This 
  species 
  differs 
  from 
  Tretocycloecia 
  multiporosa 
  in 
  

   its 
  much 
  smaller 
  mesopores. 
  It 
  differs 
  from 
  Heteropora 
  keepingi 
  

   Gregory, 
  1909, 
  which 
  has 
  a 
  similar 
  exterior 
  aspect, 
  in 
  its 
  much 
  smaller 
  

   zoarium, 
  and 
  in 
  its 
  smaller 
  zooecial 
  diameter 
  (0.09 
  and 
  not 
  0.15 
  mm.). 
  

  

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

   (common) 
  . 
  

  

  Cotypes.— 
  Cat. 
  No. 
  69940, 
  U.S.N.M. 
  

  

  