﻿E. 
  Bose 
  — 
  Ammonoids. 
  

  

  Oi 
  

  

  evolute, 
  one 
  of 
  them 
  more 
  than 
  the 
  other. 
  In 
  both 
  the 
  

   venter 
  is 
  much 
  more 
  rounded 
  and 
  the 
  cross-section 
  is 
  

   more 
  subelliptical 
  than 
  crescent-shaped. 
  The 
  ornamen- 
  

   tation 
  is 
  very 
  similar 
  in 
  both, 
  consisting 
  of 
  fine 
  radial 
  

   costse 
  on 
  the 
  nmbilical 
  wall 
  which 
  scarcely 
  swell 
  into 
  fine 
  

   nodules 
  on 
  the 
  umbilical 
  shoulder; 
  from 
  each 
  of 
  these 
  

   start 
  two 
  fine 
  costae, 
  which 
  run 
  across 
  the 
  venter 
  curving 
  

   strongly 
  forward. 
  No 
  spiral 
  lines 
  were 
  observed, 
  even 
  

   in 
  very 
  well 
  preserved 
  shells. 
  Both 
  have 
  three 
  to 
  four 
  

   constrictions 
  on 
  the 
  external 
  whorl 
  which 
  curve 
  toward 
  

   the 
  front. 
  The 
  septa 
  are 
  of 
  the 
  common 
  gastrioceran 
  

   type. 
  The 
  differences 
  between 
  the 
  two 
  species 
  are 
  not 
  

   very 
  great, 
  it 
  being 
  even 
  possible 
  that 
  both 
  represent 
  

   variations 
  of 
  the 
  same 
  type. 
  I 
  do 
  not 
  know 
  of 
  any 
  spe- 
  

   cies 
  very 
  similar 
  to 
  these 
  two 
  although 
  one 
  might 
  com- 
  

   pare 
  them 
  to 
  a 
  certain 
  degree 
  with 
  Gastrioceras 
  welleri. 
  

  

  Quite 
  different 
  from 
  the 
  foregoing 
  species 
  is 
  another 
  

   one 
  which 
  seems 
  to 
  be 
  related 
  to 
  Gastrioceras 
  Illinois 
  ense 
  

   Miller 
  and 
  Gurley 
  although 
  it 
  is 
  much 
  less 
  evolute. 
  This 
  

   species 
  is 
  characterized 
  by 
  strongly 
  rounded 
  flanks 
  and 
  

   venter, 
  very 
  narrow 
  and 
  deep 
  umbilicus 
  with 
  a 
  well 
  

   round 
  border, 
  nearly 
  semicircular 
  cross-section, 
  and 
  the 
  

   complete 
  absence 
  of 
  nodules 
  on 
  the 
  umbilical 
  border. 
  

   The 
  ornamentation 
  consists 
  of 
  fine 
  radial 
  striae 
  which 
  

   begin 
  on 
  the 
  umbilical 
  wall, 
  bifurcate 
  on 
  the 
  flank 
  and 
  

   are 
  slightly 
  curved 
  forward 
  on 
  the 
  venter. 
  Each 
  volu- 
  

   tion 
  shows 
  four 
  deep 
  constrictions 
  which 
  are 
  only 
  very 
  

   slightly 
  curved 
  forward 
  on 
  the 
  venter. 
  The 
  septa 
  are 
  

   of 
  the 
  common 
  gastrioceran 
  type. 
  

  

  The 
  nearest 
  Carboniferous 
  form 
  is 
  probably 
  G. 
  illi- 
  

   noisense, 
  but 
  it 
  is 
  much 
  more 
  globose 
  than 
  our 
  species. 
  

  

  In 
  its 
  external 
  shape 
  our 
  species 
  resembles 
  rather 
  sur- 
  

   prisingly 
  the 
  very 
  young 
  individuals 
  of 
  Gastrioceras 
  

   roadense 
  Bose 
  7 
  from 
  the 
  lower 
  Permian 
  of 
  the 
  Glass 
  

   Mountains, 
  Texas, 
  although 
  the 
  adults 
  of 
  this 
  species 
  are 
  

   entirely 
  different. 
  Also 
  similar 
  to 
  a 
  certain 
  degree 
  is 
  

   G. 
  modestum 
  Bose 
  from 
  the 
  lowermost 
  Permian 
  of 
  the 
  

   Glass 
  Mountains, 
  but 
  this 
  form 
  is 
  much 
  more 
  globose. 
  

  

  All 
  of 
  the 
  foregoing 
  species 
  of 
  Gastrioceras 
  are 
  ex- 
  

   tremely 
  common 
  in 
  the 
  Abo 
  beds 
  of 
  Tularosa, 
  every 
  one 
  

   of 
  them 
  being 
  represented 
  by 
  dozens 
  of 
  individuals 
  of 
  

   different 
  sizes 
  ; 
  but 
  our 
  collection 
  contains 
  several 
  other 
  

  

  7 
  Compare 
  especially 
  Bose, 
  Permo-Carboniferous 
  Ammonoids 
  of 
  the 
  Glass 
  

   Mountains, 
  Univ. 
  of 
  Texas. 
  Bull. 
  No. 
  1762, 
  pi. 
  2, 
  figs. 
  28-34, 
  1917. 
  

  

  