﻿HUDSON 
  RIVER 
  BEDS 
  NEAR 
  ALBANY 
  o79 
  

  

  numibers 
  of 
  individuals 
  that, 
  Darwin 
  writes, 
  one 
  could 
  call 
  the 
  

   present 
  age 
  that 
  of 
  the 
  cirripeds, 
  in 
  all 
  the 
  time 
  from 
  the 
  Devonic 
  

   to 
  the 
  Upper 
  Jurassic. 
  The 
  long 
  suppression 
  of 
  the 
  mammals 
  in 
  

   Mesozoic 
  time 
  and 
  their 
  sudden 
  rise 
  at 
  the 
  beginning 
  of 
  the 
  

   Cenozoic 
  time 
  seems 
  to 
  be 
  an 
  analogous 
  case 
  from 
  the 
  terrestrial 
  

   fauna. 
  

  

  The 
  valves 
  have 
  been 
  tentatively 
  described 
  by 
  terms 
  of 
  such 
  

   valves 
  of 
  Pollicipes 
  and 
  Scalpellum 
  as 
  they 
  most 
  

   resemble, 
  with 
  which 
  it 
  is 
  not 
  so 
  much 
  intended 
  to 
  assert 
  their 
  

   actual 
  homology 
  as 
  to 
  designate 
  them 
  by 
  names, 
  and 
  to 
  emphasize 
  

   their 
  great 
  similarity 
  to 
  the 
  parts 
  of 
  the 
  capitula 
  referred 
  to. 
  

  

  1 
  Tergum. 
  Convex, 
  elongate 
  subrhomboidal 
  to 
  subtrian- 
  

   gular, 
  as 
  the 
  upper 
  and 
  lower 
  carinal 
  margins 
  blend 
  into 
  each 
  

   other. 
  Carinal 
  margin 
  the 
  longest, 
  rounded; 
  scutal 
  margin 
  

   gently 
  rounded, 
  about 
  twice 
  as 
  long 
  as 
  the 
  occludent 
  margin. 
  

   Occludent 
  margin 
  and 
  upper 
  part 
  of 
  carinal 
  margin 
  meet 
  at 
  an 
  

   angle 
  of 
  over 
  45°, 
  qccludent 
  and 
  scutal 
  margins 
  at 
  about 
  135°. 
  

   From 
  the 
  apex 
  to 
  the 
  sharp 
  basal 
  angle, 
  a 
  strongly 
  projecting, 
  

   angular, 
  strongly 
  curved 
  conspicuous 
  ridge 
  runs 
  at 
  about 
  one 
  

   fourth 
  of 
  the 
  entire 
  width 
  of 
  the 
  valve 
  from 
  the 
  carinal 
  margin; 
  

   the 
  surface 
  slopes, 
  apparently 
  on 
  account 
  of 
  lateral 
  compression, 
  

   much 
  steeper 
  away 
  on 
  the 
  carinal 
  side. 
  A 
  wide 
  depression 
  with 
  

   a 
  central, 
  broad 
  but 
  low, 
  slightly 
  curved 
  ridge 
  extends 
  from 
  the 
  

   apex 
  to 
  the 
  middle 
  of 
  the 
  scutal 
  margin. 
  

  

  The 
  surface 
  is 
  covered 
  with 
  unequal, 
  somewhat 
  lamellose 
  

   growth 
  lines, 
  running 
  parallel 
  to 
  the 
  base 
  of 
  the 
  valve. 
  Where 
  

   the 
  shell 
  has 
  become 
  exfoliated, 
  regular 
  rows 
  of 
  pustules 
  running 
  

   parallel 
  to 
  the 
  keel 
  become 
  visible. 
  These 
  probably 
  represent 
  a 
  

   system 
  of 
  pores 
  within 
  the 
  corium. 
  

  

  It 
  is 
  specially 
  this 
  valve 
  that, 
  in 
  its 
  outline, 
  diagonal 
  keel, 
  

   direction 
  of 
  growth 
  lines 
  and 
  curved 
  fold 
  on 
  the 
  larger 
  face, 
  fully 
  

   agrees 
  with 
  the 
  terga 
  of 
  some 
  species 
  of 
  Pollicipes. 
  

  

  2 
  Carina. 
  Lanceolate 
  fragments 
  are 
  thought 
  to 
  have 
  been 
  

   part 
  of 
  the 
  carina. 
  The 
  fragment 
  figured 
  apparently 
  had 
  two 
  

   equal 
  wings 
  and 
  a 
  median, 
  highly 
  prominent, 
  angular 
  keel 
  (an- 
  

  

  