﻿art. 
  25 
  GENERA 
  SIPHOGENERINA 
  AND 
  PAVONINA 
  CUSHMAN 
  6 
  

  

  Both 
  microspheric 
  and 
  megalospheric 
  forms 
  occur 
  in 
  the 
  various 
  

   species 
  of 
  this 
  genus. 
  In 
  the 
  microspheric 
  form 
  the 
  early 
  chambers 
  

   are 
  biserial 
  or 
  triserial, 
  and 
  there 
  is 
  usually 
  a 
  considerable 
  number 
  of 
  

   them 
  before 
  the 
  adult 
  uniserial 
  development 
  takes 
  place. 
  In 
  the 
  

   megalospheric 
  form 
  the 
  uniserial 
  condition 
  is 
  taken 
  on 
  much 
  earlier, 
  

   after 
  only 
  a 
  few 
  of 
  the 
  triserial 
  or 
  biserial 
  chambers 
  are 
  developed. 
  

  

  In 
  the 
  present 
  ocean 
  the 
  species 
  are 
  found 
  in 
  the 
  Indo-Pacific 
  most 
  

   abundantly, 
  but 
  also 
  in 
  the 
  Western 
  Atlantic 
  and 
  the 
  Mediterranean. 
  

   In 
  the 
  fossil 
  condition 
  the 
  genus 
  occurs 
  in 
  the 
  Tertiary 
  as 
  noted 
  under 
  

   the 
  various 
  species. 
  

  

  Halkyard 
  in 
  his 
  paper 
  edited 
  by 
  Heron- 
  Allen 
  and 
  Earland 
  5 
  places 
  

   Siphogenerina 
  as 
  a 
  subgenus 
  of 
  Bigenerina. 
  The 
  relationships, 
  how- 
  

   ever, 
  seen 
  to 
  be 
  with 
  Uvigerina 
  and 
  the 
  Lagenidae. 
  In 
  microspheric 
  

   specimens 
  of 
  Siphogenerina 
  hifrons 
  the 
  early 
  chambers 
  sometimes 
  

   show 
  a 
  decidedly 
  coiled 
  character, 
  linking 
  the 
  early 
  development 
  of 
  

   Siphogenerina 
  with 
  coiled 
  forms 
  like 
  that 
  of 
  Cristellaria. 
  

  

  A 
  rough 
  key 
  is 
  given 
  to 
  the 
  species 
  of 
  the 
  genus 
  treated 
  here: 
  

  

  A 
  KEY 
  TO 
  THE 
  SPECIES 
  OF 
  SIPHOGENERINA 
  

  

  Test 
  not 
  compressed: 
  

   Costate 
  — 
  

  

  Costae 
  few 
  and 
  prominent 
  — 
  

  

  Costae 
  more 
  prominent 
  than 
  suture 
  lines 
  — 
  

  

  Test 
  large 
  and 
  fusiform 
  S. 
  collomi 
  

  

  Test 
  tapering 
  throughout 
  — 
  

   Costae 
  high, 
  lamellate 
  — 
  

  

  Costae 
  10 
  or 
  less 
  S. 
  raphanus 
  

  

  Costae 
  15 
  or 
  more 
  S. 
  reedi 
  

  

  Costae, 
  low, 
  not 
  lamellate 
  S. 
  kleinpelli 
  

  

  Costae 
  less 
  prominent 
  than 
  suture 
  lines 
  S. 
  branneri 
  

  

  Costae 
  numerous 
  and 
  prominent 
  — 
  

  

  Neck 
  short 
  S. 
  striata, 
  var. 
  curta 
  

  

  Neck 
  long 
  and 
  slender 
  S. 
  irregularis 
  

  

  Costae 
  very 
  numerous, 
  not 
  prominent 
  S. 
  striatula 
  

  

  Lamellate 
  — 
  

  

  Lamellae 
  very 
  prominent, 
  not 
  spinose 
  S 
  lamellata 
  

  

  Lamellae 
  less 
  prominent, 
  spinose 
  near 
  base 
  S. 
  spinosa 
  

  

  Smooth 
  — 
  

  

  Test 
  slender 
  and 
  elongate 
  S. 
  columellaris 
  

  

  Test 
  short 
  and 
  stout 
  S. 
  hughesi 
  

  

  Coarsely 
  punctate 
  S. 
  dimorpha 
  

  

  Spinose'or 
  hispid 
  S. 
  virgula 
  

  

  Slender, 
  early 
  portion 
  costate, 
  middle 
  spinose, 
  later 
  part 
  smooth. 
  S. 
  mexicana 
  

   Test 
  compressed: 
  

  

  Short, 
  stout, 
  sides 
  deeply 
  depressed 
  S. 
  bifrons 
  

  

  Elongate,j3lender, 
  sides 
  not 
  depressed 
  S. 
  advena 
  

  

  » 
  Mem. 
  Proc. 
  Manchester 
  Lit. 
  Philos. 
  Soc, 
  vol. 
  62, 
  pt. 
  2, 
  1919. 
  p. 
  37. 
  

  

  