﻿904 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  In 
  Isotrypa 
  conjunctiva 
  and 
  TJnitrypa 
  pernodosa 
  the 
  connect- 
  

   ing 
  processes 
  are 
  at 
  alout 
  the 
  same 
  distance 
  apart, 
  hut 
  there 
  is 
  

   no 
  similarity 
  in 
  the 
  appearance 
  of 
  the 
  fronds 
  as 
  would 
  he 
  the 
  

   49 
  case 
  if 
  they 
  were 
  of 
  the 
  same 
  genera; 
  on 
  the 
  

  

  contrary, 
  the 
  fronds 
  are 
  very 
  dissimilar 
  in 
  

   appearance. 
  The 
  carina? 
  and 
  connecting 
  

   processes 
  of 
  Isotrypa 
  resemble 
  in 
  a 
  very 
  

   marked 
  degree 
  the 
  noncelluliferous 
  face 
  of 
  

   some 
  fenestelloid 
  form; 
  while 
  in 
  U. 
  perno- 
  

   dosa 
  they 
  have 
  the 
  appearance 
  of 
  the 
  mouths 
  

   of 
  large 
  oblique 
  cells. 
  Sometimes 
  the 
  summits 
  

   of 
  the 
  carina? 
  are 
  not 
  continuous, 
  and 
  that 
  

   s 
  urface 
  of 
  the 
  frond 
  has 
  very 
  much 
  the 
  ap- 
  

   pearance 
  of 
  some 
  forms 
  of 
  Alveolites. 
  

   If 
  the 
  unitrypic 
  face^of^a 
  frond 
  be 
  ground 
  down 
  a 
  little 
  it 
  will 
  

   be 
  seen 
  that 
  each 
  carina 
  and 
  scala 
  consists 
  of 
  two 
  thin 
  plates 
  

   united 
  at 
  the 
  summit. 
  In 
  a 
  section 
  the 
  unitrypic 
  character 
  

   would 
  seem 
  to 
  be 
  due 
  to 
  ajseries 
  of 
  tubes 
  in 
  contact 
  or 
  nearly 
  

   so, 
  and 
  coalescing 
  at 
  the 
  summit. 
  This 
  feature 
  is 
  illustrated 
  

   in 
  figure 
  49. 
  

  

  HEMITRYPA, 
  Phillips. 
  

  

  In 
  1841, 
  Prof. 
  John 
  Phillips 
  (Palseozoic 
  Fossils 
  of 
  Cornwall, 
  

   Devon 
  and 
  West 
  Somerset) 
  formed 
  the 
  germs 
  Hemitrypa. 
  

   ("Ety. 
  =7){it(Ta)s, 
  half 
  rpuTia, 
  perforation"), 
  one 
  species 
  of 
  which, 
  

   Hemitrypa 
  oculata 
  (p. 
  27, 
  pi. 
  13, 
  fig. 
  38,) 
  he 
  describes 
  as 
  follows 
  : 
  

  

  " 
  Character, 
  a 
  thin 
  lamina 
  of 
  coral 
  expanded 
  in 
  a 
  cup 
  form 
  

   mass 
  ; 
  external 
  surface 
  wholly 
  covered 
  with 
  numerous 
  round 
  

   pores 
  or 
  cells, 
  radiating 
  from 
  a 
  center 
  and 
  associated 
  in 
  double 
  

   rows 
  which 
  near 
  the 
  center 
  undergo 
  frequent 
  divisions 
  so 
  as 
  to 
  

   form 
  two 
  such 
  (double) 
  rows. 
  Internal 
  surface 
  marked 
  by 
  radi- 
  

   ating 
  ridges 
  corresponding 
  to 
  the 
  external 
  interstices 
  between 
  

   the 
  rows 
  ; 
  between 
  these 
  ridges 
  are 
  many 
  oval 
  depressions, 
  which 
  

   penetrate 
  only 
  half 
  through 
  the 
  substance 
  of 
  the 
  coral, 
  and 
  nowhere 
  

   reach 
  the 
  outer 
  face. 
  

  

  " 
  It 
  grows 
  to 
  the 
  size 
  of 
  two 
  or 
  three 
  inches 
  in 
  diameter. 
  

   The 
  internal 
  face 
  is 
  like 
  that 
  of 
  some 
  Fenestella, 
  but 
  the 
  

   peculiarities 
  of 
  the 
  external 
  surface 
  seem 
  to 
  demand 
  generic 
  

   separation. 
  The 
  specimens 
  are 
  extremely 
  perfect." 
  

  

  