﻿ACADEMY 
  OF 
  SCIENCES. 
  123 
  

  

  but 
  much 
  less 
  extreme, 
  and 
  scarcely 
  definable, 
  as 
  they 
  run 
  together 
  very 
  closely. 
  

   This 
  is 
  a 
  consequence 
  of 
  its 
  distribution 
  being 
  continuous 
  from 
  north 
  to 
  south 
  

   along 
  a 
  mountain 
  range, 
  and 
  not 
  interrupted 
  by 
  alternating 
  mountains, 
  valleys, 
  

   and 
  bays, 
  as 
  is 
  that 
  of 
  the 
  preceding. 
  It 
  is 
  always 
  recognisable 
  by 
  fixed 
  char- 
  

   acters 
  permanent 
  through 
  great 
  extremes 
  of 
  size. 
  

  

  At 
  the 
  south 
  end 
  of 
  the 
  range 
  of 
  tudiadata 
  we 
  meet 
  with 
  another 
  species, 
  

   in 
  range 
  somewhat 
  intermingled 
  with 
  it, 
  but 
  always 
  distinct, 
  viz 
  : 
  A. 
  Kellettii 
  

   Fbs., 
  which 
  centres 
  around 
  San 
  Diego 
  Bay 
  and 
  the 
  neighboring 
  islands, 
  from 
  

   lat. 
  34° 
  southward 
  to 
  lat. 
  28°, 
  or 
  perhaps 
  26°, 
  in 
  Lower 
  California, 
  four 
  hun- 
  

   dred 
  or 
  five 
  hundred 
  miles. 
  The 
  various 
  forms 
  found 
  within 
  this 
  vast 
  range, 
  

   and 
  which 
  have 
  been 
  described 
  as 
  KeUeitii, 
  redimita, 
  Tryoni, 
  intercisa, 
  crehris- 
  

   triata, 
  and 
  Stearnsiana. 
  pass 
  so 
  insensibly 
  from 
  one 
  to 
  another 
  that 
  they 
  must 
  be 
  

   considered 
  merely 
  varieties 
  analogous 
  to 
  those 
  of 
  Calif 
  orrdensU. 
  The 
  most 
  

   northern 
  is 
  the 
  most 
  difierent 
  from 
  the 
  type 
  which 
  was 
  from 
  the 
  most 
  southern 
  

   part 
  of 
  their 
  range, 
  but 
  intermediate 
  forms 
  connect 
  them 
  all. 
  

  

  The 
  parallel 
  between 
  the 
  varieties 
  of 
  the 
  two 
  species 
  is 
  well 
  shown 
  by 
  the 
  

   following 
  table 
  : 
  

  

  A. 
  Form 
  elevated, 
  imperforate. 
  Inhabit 
  cool, 
  foggy 
  exposures. 
  

   h. 
  vincfa 
  Val 
  Tri/oni 
  Newc. 
  

  

  c. 
  riemorivnga 
  Val 
  redimita 
  W. 
  G. 
  B. 
  

  

  a. 
  CA 
  LIFORNIENSIS 
  Lea 
  KELLETTII 
  Fbs. 
  

  

  B. 
  More 
  depressed, 
  perforate. 
  From 
  warmer 
  localities. 
  

  

  d. 
  ramentosa 
  Gld. 
  crebrisiriata 
  Newc. 
  

  

  e. 
  reticulata 
  Pf. 
  iidercisa 
  Kewc. 
  

  

  f. 
  Bridgenii 
  Newc 
  Stearnsiana 
  Gabb. 
  

  

  Though 
  of 
  course 
  not 
  strictly 
  parallel, 
  many 
  points 
  of 
  resemblance 
  can 
  be 
  

   seen 
  between 
  the 
  forms 
  thus 
  compared. 
  Thus 
  the 
  varieties 
  d. 
  and 
  e. 
  of 
  each 
  

   have 
  similar 
  relations 
  inter 
  se 
  as 
  to 
  sculpture, 
  while 
  / 
  is 
  in 
  each 
  very 
  similar 
  to 
  

   the 
  type 
  ; 
  the 
  "circular" 
  arrangement 
  being 
  well 
  represented 
  in 
  each 
  group. 
  

  

  All 
  these 
  banded 
  species 
  and 
  varieties 
  are 
  connected 
  so 
  closely 
  together 
  by 
  

   their 
  banded 
  character, 
  that 
  a 
  common 
  origin 
  in 
  the 
  dim 
  periods 
  of 
  the 
  past 
  

   seems 
  highly 
  probable, 
  and 
  yet 
  their 
  parallelism 
  with 
  another 
  large 
  series 
  exist- 
  

   ing 
  in 
  the 
  same 
  regions, 
  but 
  always 
  distinguishable, 
  indicates 
  that 
  some 
  common 
  

   physiological 
  law, 
  still 
  unknown, 
  is 
  connected 
  with 
  this 
  character. 
  In 
  the 
  form 
  

   of 
  shell 
  and 
  animal, 
  as 
  well 
  as 
  in 
  its 
  anatomy, 
  they 
  seem 
  more 
  closely 
  connected 
  

   with 
  the 
  Lower 
  Californian 
  group 
  embracing 
  areolata, 
  PandorcE, 
  levit, 
  etc., 
  

   which 
  vary 
  from 
  colorless 
  to 
  many-banded 
  or 
  blotched, 
  showing 
  a 
  relationship 
  

   similar 
  to 
  that 
  held 
  by 
  "Jrionta 
  candidisdma 
  " 
  of 
  Palestine 
  to 
  A. 
  arbustorum 
  

   of 
  Europe, 
  a 
  species 
  between 
  Califonnensis 
  and 
  Kelletlii. 
  

  

  II. 
  LY 
  SINGE 
  H. 
  and 
  A. 
  Adams. 
  

  

  A 
  comparison 
  of 
  the 
  distribution 
  of 
  the 
  species 
  which 
  I 
  have 
  referred 
  to 
  this 
  

   group 
  with 
  that 
  of 
  the 
  Aiiontas, 
  presents 
  one 
  very 
  striking 
  difference 
  at 
  first 
  

  

  