﻿82 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL, 
  MUSEUM 
  vol.67 
  

  

  The 
  Z. 
  magnoliaeformis 
  type 
  specimen 
  is 
  from 
  Huntsville, 
  Ala- 
  

   bama, 
  in 
  what 
  is 
  now 
  known 
  as 
  the 
  Gasper 
  formation 
  of 
  the 
  upper 
  

   Chester, 
  where 
  the 
  species 
  occurs 
  numerously 
  ; 
  while 
  Z. 
  wort 
  herd, 
  as 
  

   found 
  in 
  several 
  localities 
  in 
  Illinois 
  and 
  Kentucky, 
  is 
  from 
  the 
  next 
  

   higher 
  formation 
  of 
  the 
  Chester, 
  Glen 
  Dean 
  of 
  Kentucky 
  and 
  Okaw 
  

   of 
  Illinois. 
  Numerous 
  specimens 
  of 
  both 
  forms 
  enable 
  me 
  to 
  make 
  

   a 
  close 
  comparison 
  as 
  to 
  the 
  corresponding 
  characters. 
  

  

  From 
  the 
  Huntsville 
  locality, 
  Gasper 
  formation, 
  there 
  are 
  about 
  100 
  

   specimens, 
  including 
  7 
  complete 
  crowns. 
  Measurement 
  of 
  these 
  for 
  

   height 
  of 
  crown 
  and 
  diameter 
  of 
  calyx 
  at 
  top 
  of 
  radials 
  gives 
  an 
  

   average 
  of 
  57 
  mm. 
  height 
  (ranging 
  from 
  45 
  to 
  68), 
  and 
  19 
  mm. 
  

   diameter 
  (17 
  to 
  21). 
  Out 
  of 
  the 
  total, 
  79 
  specimens 
  have 
  post. 
  B 
  

   broadly 
  truncate, 
  RA 
  large 
  and 
  broad, 
  producing 
  a 
  more 
  or 
  less 
  wide 
  

   anal 
  area 
  ; 
  12 
  have 
  post. 
  B 
  acuminate 
  as 
  in 
  the 
  type 
  of 
  Z. 
  wortheni 
  — 
  

   a 
  narrow 
  anal 
  area; 
  and 
  9 
  are 
  in 
  an 
  intermediate 
  stage. 
  Thus 
  with 
  

   80 
  per 
  cent 
  of 
  the 
  specimens 
  having 
  post. 
  B 
  broadly 
  truncate, 
  it 
  may 
  

   be 
  said 
  in 
  general 
  that 
  the 
  earlier, 
  Gasper, 
  form 
  has 
  a 
  wide 
  anal 
  

   area. 
  

  

  From 
  the 
  later 
  formation, 
  Glen 
  Dean, 
  at 
  the 
  most 
  prolific 
  locality, 
  

   Sloan's 
  Valley, 
  Pulaski 
  County, 
  Kentucky, 
  there 
  are 
  65 
  specimens, 
  

   among 
  which 
  are 
  22 
  complete 
  crowns. 
  Measurement 
  of 
  these 
  yields 
  

   an 
  average 
  of 
  30 
  mm. 
  height 
  (16 
  to 
  40) 
  and 
  13 
  mm. 
  diameter 
  of 
  

   calyx 
  (7 
  to 
  17). 
  Thus 
  while 
  on 
  an 
  average 
  the 
  absolute 
  height 
  of 
  

   crown 
  is 
  about 
  twice 
  as 
  great 
  in 
  Z. 
  magnoliaeformis 
  as 
  in 
  Z. 
  wortheni, 
  

   its 
  relative 
  height 
  to 
  the 
  width 
  of 
  calyx 
  is 
  also 
  much 
  greater, 
  being 
  

   as 
  3 
  by 
  1 
  to 
  2.3 
  by 
  1. 
  Of 
  the 
  Sloan's 
  Valley 
  specimens 
  37 
  have 
  the 
  post. 
  

   B 
  acuminate, 
  with 
  a 
  narrow 
  RA 
  passing 
  down 
  alongside 
  post. 
  B 
  

   almost 
  to 
  a 
  connection 
  with 
  IBB. 
  In 
  the 
  remainder 
  the 
  post. 
  B 
  is 
  

   truncate 
  to 
  a 
  varying 
  extent, 
  from 
  18 
  having 
  a 
  very 
  narrow 
  connection 
  

   with 
  the 
  succeeding 
  anal, 
  being 
  practically 
  acuminate, 
  to 
  10 
  in 
  which 
  

   the 
  truncation 
  is 
  as 
  broad 
  as 
  in 
  the 
  Huntsville 
  specimens, 
  with 
  some 
  

   intermediate 
  stages 
  ; 
  but 
  in 
  most 
  of 
  them 
  the 
  RA 
  is 
  an 
  elongate 
  plate, 
  

   and 
  the 
  anal 
  area 
  in 
  85 
  per 
  cent 
  of 
  the 
  specimens 
  should 
  be 
  classed 
  

   as 
  narrow. 
  

  

  These 
  data 
  seemed 
  to 
  furnish 
  two 
  good 
  characters 
  for 
  distinguish- 
  

   ing 
  the 
  species, 
  until 
  I 
  was 
  tempted 
  to 
  inspect 
  the 
  anal 
  side 
  of 
  

   Troost's 
  type 
  by 
  removing 
  the 
  hard 
  matrix 
  by 
  which 
  it 
  was 
  en- 
  

   closed, 
  and 
  found 
  that 
  it 
  has 
  a 
  pointed 
  post. 
  B, 
  and 
  thus 
  falls 
  under 
  

   the 
  exception 
  instead 
  of 
  the 
  general 
  rule. 
  Nevertheless, 
  we 
  are 
  

   warranted 
  by 
  the 
  great 
  preponderance 
  of 
  the 
  evidence 
  in 
  claiming 
  the 
  

   wide 
  anal 
  area 
  as 
  one 
  of 
  the 
  characters 
  for 
  Z. 
  magnoliaeformis, 
  

   when 
  correlated 
  with 
  the 
  larger 
  crown. 
  

  

  From 
  the 
  foregoing 
  facts 
  it 
  results 
  that 
  the 
  decisive 
  difference 
  

   between 
  the 
  two 
  species 
  as 
  stated 
  by 
  Hall 
  holds 
  good 
  in 
  the 
  greater 
  

  

  