﻿20 
  

  

  PROCEEDINGS 
  OF 
  THE 
  NATIONAL. 
  MUSEUM 
  

  

  Rarely 
  the 
  zonal 
  lines 
  become 
  transformed 
  into 
  epithecal 
  lines 
  in 
  

   a 
  portion 
  of 
  their 
  length 
  (Ceriopora 
  aequipedis). 
  

  

  A 
  zonal 
  line 
  is 
  formed 
  by 
  divers 
  elements, 
  diaphragms, 
  transverse 
  

   bands 
  of 
  vesicles, 
  and 
  at 
  the 
  intersection 
  of 
  the 
  zooecial 
  walls 
  by 
  

   large 
  vesicles 
  with 
  thicker 
  walls. 
  They 
  correspond, 
  therefore, 
  along 
  

   the 
  entire 
  extent 
  of 
  their 
  length 
  to 
  the 
  tubes 
  contracted 
  and 
  with 
  

   denser 
  calcification. 
  They 
  may 
  be 
  only 
  potential 
  and 
  manifested 
  

   only 
  by 
  simultaneous 
  deformations 
  of 
  the 
  tubes 
  (Defranciopora) 
  . 
  

  

  Fig. 
  5.— 
  Ceriopora 
  ovoidea, 
  new 
  species. 
  A. 
  Meridian 
  section, 
  X 
  10, 
  through 
  a 
  zoarium 
  with 
  definite 
  

   zonal 
  lines. 
  Lower 
  Cretacious 
  (Valangian): 
  Sainte-Croix, 
  Switzerland 
  

  

  We 
  are 
  ignorant 
  of 
  the 
  significance 
  of 
  the 
  zonal 
  lines. 
  They 
  per- 
  

   haps 
  correspond 
  to 
  the 
  arrests 
  of 
  growth 
  occasioned 
  by 
  the 
  seasons. 
  

   Their 
  arrangement 
  in 
  the 
  ensemble 
  of 
  colonial 
  architecture 
  seems 
  to 
  

   be 
  more 
  a 
  question 
  of 
  mathematics 
  than 
  of 
  biology. 
  

  

  Zooecial 
  walls. 
  — 
  The 
  walls 
  of 
  the 
  tubes 
  are 
  very 
  variable 
  in 
  thick- 
  

   ness 
  and 
  in 
  structure, 
  characteristics 
  which 
  determine 
  the 
  species. 
  

   Two 
  different 
  species 
  have 
  always 
  a 
  different 
  vesicular 
  constitution. 
  

  

  