﻿74 
  

  

  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  

  

  Affinities. 
  — 
  This 
  species 
  differs 
  from 
  Diplocava 
  incondita 
  in 
  its 
  

   larger 
  zoarium, 
  in 
  the 
  smaller 
  measurements, 
  and 
  in 
  the 
  considerable 
  

   separation 
  of 
  the 
  groups 
  of 
  large 
  tubes. 
  It 
  differs 
  from 
  Diplocava 
  

   globulosa 
  in 
  its 
  arborescent 
  zoarium 
  and 
  in 
  the 
  separation 
  of 
  the 
  

   groups 
  of 
  larger 
  tubes. 
  

  

  The 
  sections 
  show 
  the 
  usual 
  structure 
  of 
  Diplocava. 
  They 
  indi- 
  

   cate 
  that 
  the 
  central 
  colony 
  may 
  be 
  covered 
  over 
  by 
  an 
  exterior 
  

   incrusting 
  lamella. 
  

  

  Occurrence. 
  — 
  Lower 
  Creta- 
  

   ceous 
  (Valangian) 
  : 
  Sainte- 
  

   Croix 
  (Vaud), 
  Switzerland 
  

   (very 
  rare). 
  

  

  Cotype.—C&t. 
  No. 
  69927, 
  

   U.S.N.M. 
  

  

  DIPLOCAVA 
  GLOBULOSA, 
  new 
  species 
  

  

  Plate 
  11, 
  figs. 
  9-11 
  

  

  Description. 
  — 
  The 
  zoari- 
  

   um 
  is 
  a 
  globular 
  multilamel- 
  

   lar 
  mass 
  ; 
  it 
  is 
  free 
  or 
  incrusts 
  

   shells 
  (Semimulticava) 
  . 
  The 
  

   large 
  cells 
  are 
  grouped 
  in 
  or- 
  

   bicular 
  spaces 
  which 
  are 
  

   somewhat 
  convex. 
  The 
  

   small 
  zooecia 
  form 
  zones 
  of 
  

   more 
  or 
  less 
  width 
  around 
  

   each 
  group 
  of 
  large 
  orifices. 
  

   Measurements. 
  — 
  Diameter 
  

   interior, 
  of 
  large 
  tubes, 
  0.16 
  

   mm.; 
  diameter 
  interior 
  of 
  

   small 
  tubes, 
  0.10 
  mm.; 
  di- 
  

   ameter 
  of 
  zoarium, 
  10 
  mm. 
  

   Structure. 
  — 
  In 
  sectioning 
  

   the 
  elliptical 
  zoarium 
  along 
  

   the 
  large 
  axis 
  one 
  would 
  ex- 
  

   <* 
  m 
  I 
  pect 
  to 
  cut 
  the 
  zooecia 
  along 
  

   their 
  length, 
  but 
  this 
  does 
  

   not 
  happen, 
  as 
  the 
  section 
  cuts 
  only 
  the 
  expanded 
  extremity 
  of 
  the 
  

   tubes. 
  In 
  this 
  genus 
  the 
  direction 
  of 
  the 
  tubes 
  is 
  absolutely 
  inde- 
  

   pendent 
  of 
  the 
  zoarial 
  form 
  and 
  the 
  direction 
  can 
  only 
  be 
  surmised 
  

   from 
  the 
  exterior. 
  As 
  may 
  be 
  readily 
  observed 
  , 
  the 
  large 
  tubes 
  occur 
  

   only 
  in 
  the 
  convex 
  portions, 
  while 
  the 
  small 
  tubes 
  are 
  limited 
  to 
  the 
  

   concave 
  portions; 
  the 
  difference 
  between 
  them 
  is 
  of 
  little 
  importance. 
  

   In 
  tangential 
  section 
  the 
  tubes 
  are 
  rounded 
  and 
  included 
  in 
  the 
  

   thick 
  hexagonal 
  walls. 
  The 
  difference 
  in 
  size 
  between 
  the 
  large 
  and 
  

  

  