﻿E. 
  Bose 
  — 
  Ammonoids. 
  59 
  

  

  istic 
  of 
  the 
  upper 
  Pennsylvania]!, 
  notwithstanding 
  that 
  

   J. 
  P. 
  Smith 
  has 
  described 
  some 
  species 
  from 
  the 
  Missis- 
  

   sippian 
  8 
  which 
  he 
  doubtfully 
  refers 
  to 
  this 
  genus. 
  Still 
  

   more 
  important 
  is 
  the 
  circumstance 
  that 
  our 
  Goniolobo- 
  

   ceras 
  is 
  very 
  intimately 
  related 
  to 
  G. 
  welleri 
  from 
  the 
  

   upper 
  Pennsylvanian 
  (Uralian) 
  of 
  Texas 
  (about 
  600 
  feet 
  

   below 
  the 
  Permian 
  contact) 
  ; 
  this 
  makes 
  it 
  almost 
  certain 
  

   that 
  they 
  are 
  more 
  or 
  less 
  of 
  the 
  same 
  age. 
  

  

  Gastrioceras 
  is 
  a 
  genus 
  which 
  occurs 
  throughout 
  the 
  

   Carboniferous 
  and 
  the 
  Permian, 
  but 
  the 
  groups 
  which 
  are 
  

   represented 
  in 
  our 
  collection 
  distinctly 
  belong 
  to 
  Penn- 
  

   sylvanian 
  types 
  and 
  especially 
  to 
  those 
  from 
  the 
  Uralian. 
  

   In 
  the 
  Permian 
  most 
  of 
  the 
  species 
  of 
  Gastrioceras 
  

   belong 
  to 
  the 
  very 
  characteristic 
  group 
  of 
  G. 
  zitteli, 
  while 
  

   the 
  Pennsylvanian 
  types 
  are 
  rather 
  rare 
  in 
  this 
  system. 
  

   In 
  the 
  Abo 
  sandstone 
  of 
  Tularosa, 
  on 
  the 
  contrary, 
  the 
  

   group 
  of 
  G. 
  zitteli 
  is 
  entirely 
  absent, 
  while 
  Pennsylva- 
  

   nian 
  forms 
  occur 
  in 
  abundance. 
  

  

  Thus 
  we 
  have 
  to 
  conclude 
  that 
  the 
  Abo 
  beds 
  belong 
  to 
  

   the 
  Pennsylvanian 
  and 
  that 
  they 
  belong 
  in 
  the 
  upper 
  part 
  

   of 
  this 
  system 
  (Uralian). 
  

  

  This 
  is 
  confirmed 
  by 
  still 
  another 
  fact. 
  Mr. 
  Baker, 
  

   while 
  studying 
  the 
  younger 
  Paleozoic 
  of 
  the 
  upper 
  Pecos 
  

   Valley 
  in 
  New 
  Mexico, 
  found 
  that 
  the 
  Abo 
  sandstone 
  

   there 
  rests 
  unconf 
  ormably 
  on 
  the 
  Magdalena 
  beds, 
  which 
  

   in 
  their 
  upper 
  part 
  also 
  contain 
  an 
  upper 
  Carboniferous 
  

   fauna. 
  Near 
  Pecos 
  village 
  we 
  collected 
  in 
  the 
  lowermost 
  

   Abo 
  beds 
  a 
  number 
  of 
  brachiopods 
  and 
  pelecypods 
  

   (mainly 
  Productus 
  and 
  Myalina) 
  among 
  which 
  not 
  a 
  

   single 
  Permian 
  form 
  was 
  present. 
  Unfortunately 
  the 
  

   higher 
  part 
  of 
  the 
  Abo 
  beds 
  in 
  this 
  portion 
  of 
  the 
  Pecos 
  

   valley 
  is 
  entirely 
  barren 
  of 
  fossils. 
  It 
  is 
  covered 
  by 
  the 
  

   so-called 
  Glorieta 
  sandstone, 
  the 
  age 
  of 
  which 
  was 
  un- 
  

   known 
  up 
  to 
  the 
  present, 
  but 
  Mr. 
  Baker 
  and 
  the 
  author 
  

   have 
  followed 
  the 
  formation 
  toward 
  the 
  south 
  to 
  Los 
  

   Griegos 
  and 
  the 
  Blanco 
  Canon, 
  where 
  it 
  is 
  unconform- 
  

  

  8 
  Haug, 
  Traite 
  de 
  Geologie, 
  p. 
  751, 
  wants 
  to 
  replace 
  the 
  term 
  Mississip- 
  

   pian 
  by 
  the 
  term 
  Dinantian 
  because 
  the 
  former 
  name 
  was 
  used 
  by 
  Marcou 
  

   in 
  an 
  entirely 
  different 
  sense 
  (= 
  Cambrian). 
  Haug 
  himself 
  recognizes 
  

   (p. 
  786) 
  that 
  the 
  term 
  Mississippian 
  has 
  been 
  extremely 
  well 
  chosen, 
  as 
  no 
  

   region 
  is 
  known 
  where 
  the 
  lower 
  Carboniferous 
  is 
  as 
  well 
  developed 
  as 
  in 
  

   the 
  Mississippi 
  basin. 
  It 
  seems 
  to 
  me 
  that 
  the 
  name 
  Mississippian 
  should 
  

   be 
  accepted 
  as 
  part 
  of 
  the 
  universal 
  nomenclature, 
  because 
  it 
  is 
  well 
  chosen 
  

   and 
  has 
  been 
  in 
  general 
  use 
  in 
  America 
  for 
  a 
  long 
  time. 
  Marcou 
  ; 
  s 
  use 
  

   of 
  this 
  name 
  for 
  the 
  Cambrian 
  never 
  has 
  been 
  accepted 
  and 
  should 
  simply 
  

   be 
  abandoned. 
  

  

  